Microbiology Final

Protein Synthesis inhibitors

30s Aminoglycosides Tetracyclines 50s Macrolides Chloramphenicol Lincosamides Oxazolidinones Streptogramin

Bacterial Plasma membrane

4 important functions: Active transport of molecules into the cell Energy generation by oxidative phosphorylation Contains polymerizing enzymes for synthesis of cell wall Secretion of enzymes and toxins Components Phospholipid bilayer: similar to eukaryotic cells: Except that sterols are absent Some integral and/or peripheral glyco/lipoproteins participate in transport and/or metabolism

Diagnosis of Cystoisospora belli

Demonstration of oocyst (Approx.25 × 15µm) Concentrated stool specimens and Iodine mount or Modified Acid fast stained smears

Aldehydes

Denature proteins and modify nucleic acids Glutaraldehyde: in 2% solution (Cidex) used as sterilant for heat sensitive instruments Formaldehyde - disinfectant, preservative; toxicity limits use formalin - 37% aqueous solution

Platyhelminthes

*Cestodes (Tapeworms) -Diphyllobothrium latum (Fish tapeworm) -Echinococcus granulosus (Dog tapeworm) -Taenia saginata (Beef tapeworm) -Taenia solium (Pig tapeworm) -Hymenolepis nana (Dwarf tapeworm) *Trematodes (Flukes) -Clonorchis sinensis (Chinese or oriental liver fluke) -Paragonimus westermani (Lung fluke) -Fasciolopsis buski (Giant Intestinal fluke) -Fasciola hepatica (common liver fluke) -Schistosoma spp (Blood flukes)

Fasciola hepatica

"common liver fluke" or "the sheep liver fluke'' Epidemiology: worldwide in sheep raising areas, rare in US but cases in travelers from endemic areas, Infect herbivores (mainly sheep & cattle) and humans; snail as intermediate host. Transmission: consumption of contaminated raw/undercooked Watercress/fresh water plant Morphology: Egg, Larvae, and Adult Fluke

Axial Filaments

(endoflagella) For motility Flagellin covered by outer sheath (membrane) Only found in Spirochetes

Structural Components of Bacteria

1. Cell Wall 2. Plasma Membrane 3. Cytoplasm 4. Ribosomes 5. Nucleoid 6. +/- Plasmids 7. +/- Capsule 8. +/- Biofilms 9. +/- Pili/Fimbriae 10. +/- Flagella 11. +/-Axial Filaments 12. +/- Spores

Viral Composition

A Complete virus is called a virion or a viral particle Genome + capsid = Nucleocapsid

Lac Operon

A gene system whose operator gene and three structural genes control lactose metabolism in E. coli Lactose is inhibiting the repressor, allowing the RNA polymerase to bind with the promoter, and express the genes, which synthesize lactase. Eventually, the lactase will digest all of the lactose, until there is none to bind to the repressor. The repressor will then bind to the operator, stopping the manufacture of lactase The gene product of lacZ is β-galactosidase which cleaves lactose, a disaccharide, into glucose and galactose. LacY encodes lactose permease, a protein which becomes embedded in the cytoplasmic membrane to enable transport of lactose into the cell. Finally, lacA encodes galactoside O-acetyltransferase.

Reservoir host

A host in which the infectious agent normally lives and multiplies. It acts as the source for transmission of infection to humans.

Parasite

A living organism requiring intimate prolonged contact with another living organism to meet some of its basic nutritional needs. It refers to eukaryotic pathogens.

Pathogen

A microbe that has the ability to cause disease

Antiseptic

A substance/chemical that can be applied to tissue and inhibits the growth of microorganisms.

Neurocysticercosis

A person gets cysticercosis by swallowing eggs (Remember! Not with LARVAE) found in the feces of a person who has an intestinal tapeworm. People living in the same household with someone who has a tapeworm have a much higher risk of getting cysticercosis than people who don't. People do not get cysticercosis by eating undercooked pork (i.e containing larvae). Eating undercooked pork can result in intestinal tapeworm if the pork contains larval cysts. Pigs become infected by eating tapeworm eggs in the feces of a human infected with a tapeworm (CDC)

Prophage

A phage genome that has been inserted into a specific site on the bacterial chromosome.

Lysogenic Cycle

A phage replication cycle in which the viral genome becomes incorporated into the bacterial host chromosome as a prophage and does not kill the host.

Antimetabolites

A substance that interferes with the normal metabolic processes within cells, typically by combining with enzymes or mimic an important or a required metabolite Inhibition of Folic acid Synthesis Sulfonamides (several derivatives) Trimethoprim Para-aminosalicylic acid (PAS) Dapsone

Viral neuraminidase

A type of neuraminidase found on the surface of virus (eg. Paramyxo virus, orthomyxovirus ) that enables the virus to be released from the host cell. Neuraminidases are enzymes that cleave sialic acid groups from glycoproteins and are required for influenza virus replication.

Lytic cycle

A type of viral (phage) replication cycle resulting in the release of new phages by lysis (and death) of the host cell. Eclipse phase: Entry of nucleic acid into the cell and first appearance of infectious intracellular phage particle Latent phase: Time interval between infection of a cell to the first release of infectious phage particles.

Amoebic ulcer of the penis

A very rare clinical entity. We report a case of amoebic ulcer of the glans penis in a 47- year-old male homosexual, symptomatic with severe pain and foul-smelling hemopurulent discharge of acute onset. He had received systemic antibiotics like ciprofloxacin and azithromycin prior to presentation with no improvement. Diagnosis was confirmed by wet mount microscopic examination of the discharge. The patient responded well to a course of metronidazole.

Complex virus

A virus with a complicated structure, such as a bacteriophage. Unusual morphology e.g. Poxvirus (enveloped), bacteriophage

Activation of G protein

A-B toxin causes ADP ribosylation Increase in adenylate cyclase activity - Increase in cAMP In the respiratory epithelium, the high levels of cAMP results in increased respiratory secretions and mucous production and contributes to coughing. 1. Cholera toxin (Vibrio cholerae)/Heat labile toxin (Escherichia coli) - Act on small intestine Cause watery diarrhea/secretory diarrhea 2. Pertussis toxin (Bordetella pertussis): Respiratory epithelium pathogen The high levels of cAMP results in increased respiratory secretions and mucous production and contributes to coughing.

Inactivation of EF-2

A-B toxin causes ADP ribosylation Leads to Inhibition of protein synthesis 1. Diphtheria toxin: Corynebacterium diphtheriae Upper Respiratory tract pathogen; results in cell death. Toxin can enter circulation and affect heart, kidney, nerves Toxin gene carried by temperate phage 2. Exotoxin A: Pseudomonas aeruginosa Pneumonia in cystic fibrosis patients

Pathogenesis of Ascariasis

A. Pulmonary manifestation: - pneumonitis (Loeffler's syndrome) Caused by the larvae migration through the lungs Results in accumulation of eosinophils in the lung Signs and symptoms: Dry nonproductive cough, fever chest pain, wheezing, dyspnea, rales (crackling sound) on auscultation Chest X-ray shows infiltrates B. Intestinal manifestation:- GI symptoms resulting from mechanical irritation include vague abdominal complaints - cramping, distended abdomen, intermittent loose stool and occasional nausea and vomiting. Heavy infection - Entanglement of large no. of parasite Small bowel obstruction (mostly in children) May lead to perforation, intussusception, volvulus (bowel twisted on itself) C. Adult worm migration: bile duct - cholecystitis; pancreatic duct - pancreatitis; and appendix- appendicitis

Infectious Mycoses

A. Superficial mycoses: superficial limited to outermost layers of the skin and hair. No inflammation B. Cutaneous mycoses: may extend into epidermis, invasive; hair and nail involvement C. Subcutaneous mycoses: involve dermis, subcutaneous tissues, muscle, and fascia - usually requires traumatic implantation D. Systemic mycoses: Start with localized infection such as in the lung (by inhalation); may disseminate to skin and other organs. E. Opportunistic mycoses: often normal flora or ever-present in environment, special conditions allow disease: -Suppression of normal flora: by antibacterial therapy -Diabetes -Immuno-suppression *HIV infection, use of immunosuppressive drugs etc.

Cell and tissue damage

A. Toxic products: Hydrolytic enzymes, cytolytic enzymes B. Mechanical Damage: blockage, pressure, migration of larva through tissue C. Immunopathology : Type I hypersensitivity (IgE mediated hypersensitivity): mast cell and eosinophil degranulation Type II and III type hypersensitivity: tissue damage and inflammation and scarring Type IV hypersensitivity: cell mediated; granuloma Type I: Helminthic infection, African trypanosomiasis Type II: Trypanosoma cruzi infection Type III: Malaria, Schistosomiasis, Trypanosomiasis Type IV: Leishmaniasis (Kala-azar), Schistosomiasis, Trypanosomiasis Competition for nutrition (malnutrition), cause loss of blood

Fluorescence Microscope

An optical microscope that uses fluorescence and phosphorescence instead of, or in addition to, reflection and absorption to look at organisms on a slide. Up to 2000x magnification.

Cutaneous larva migrans

Ancylostoma caninum & braziliense The lesions are erythematous, serpiginous (spreads by creeping), pruritic (extremely itchy), cutaneous eruption. IP: 1-5 days or long; Lasts for 2-10 weeks This is separate from the similar cutaneous larva currens which is caused by strongyloides.

Significance of conjugation

Antibiotic resistance, R Plasmids Plasmid carrying multiple antibiotic resistance genes Rapid spread The whole process of conjugation takes about 100 min Virulence genes Pili genes that mediate adherence to epithelial cells Exotoxins genes can be transferred.

Serological analysis

Antibody detection/titer ELISA Heamagglutination inhibition assay Neutralization tests: block cytopathic effects Western blot Rapid tests eg, for HIV Neutralization (prevention of cytopathic effect) Hemagglutination inhibition assay

Lipopolysaccharide (LPS)

Antigen - surface antigens on Gram negative bacteria Target for specific immune response Serotyping of bacteria Core polysaccharide - contributes to the integrity of membrane Conserved among related Gram negatives Lipid A - long fatty acid: Endotoxin: Inflammation, hypotension, shock some variation across species

Treatment of Malaria

Antimalarial drugs Chloroquine or quinine; For chloroquine resistant cases: mefloquine± artesunate, artemether-lumafantrine, atovaquone-proguanil Prevention and Control Chemoprophylaxis for traveler to endemic areas: Chloroquine (P. falciparum sensitive areas) Mefloquine or doxycycline (chloroquine resist. P. falciparum endemic areas) Eradications of infections Vector control: control of mosquito breeding Protection of individuals by screening/window screening, netting, protective clothing and insect repellants

Culture medium

Any material that contains the required nutrition and supports the growth of the microbes and is prepared in laboratory. It could be in liquid form - broth Solid/Semisolid - broth + a solidifying agent (agar)

Filarial worms

Any of a group of parasitic worms of the family Filariidae (phylum Nematoda) that usually require two hosts, an arthropod (the intermediate host) and a vertebrate (the primary/definitive host), to complete the life cycle. The larval phase occurs within the body of a biting insect. The mature (reproductive) phase occurs in the body of an animal bitten by the insect. Require 2 hosts: an arthropod (Intermediate host) and a vertebrate (Definitive host) Wuchereria bancrofti/ Brugia malayi - Elephantiasis Onchocerca volvulus - River blindness Loa loa - eye worm

Itch Mites

Arachnid; Small sack like body Medically important (Sarcoptes scabiei), General Properties 300-400µm length 1st and 2nd pairs of legs widely separated from 3rd and 4th. Epidemiology: Worldwide, Global prevalence of nearly 300 million cases, obligate parasite of domestic animals (eg, dogs, cats) and humans Transmission: Personal contact or by fomites causes scabies

Spiders

Arachnids; Produce venom Venomous spiders may cause: Systemic arachnidism (Neurotoxic disease) Black widow spiders and Tarantulas Intense pain and phase of agitation followed by stupor and somnolence No tissue necrosis Necrotic arachnidism (Dermonecrotic disease) Brown recluse spider Severe tissue necrosis

Fungal Cell Structure

Are Eukaryotic cells, unicellular or multicellular and have membrane bound organelles, nuclear membrane, cytoskeleton Fungal Cell membrane: Phospholipid bilayer like mammalian cells, but differs in the nature of sterol- they have ergosterol instead of cholesterol Site of action for antifungal drugs Amphotericin B and azole

Peplomers (spikes)

Are proteinaceous projections that extend from the capsid; or viral glycoproteins inserted on envelope Importance of Peplomers Attachment of the virus to host cells, act as viral attachment proteins (VAPs), Determine tissue and host specificity Some may have enzymatic activity to aid entry or exit of the virus Antigens - target for the immune system Have other useful properties—as antigens useful in classification, hemagglutination

Antimicrobial Susceptibility Testing

Are used to make the best drug of choice to treat infections Diffusion Tests Dilution Tests Automated Tests Phenotype testing/Enzyme testing Molecular tests: Genotype testing

Soil transmitted helminths

Ascaris Hookworm Whipworm Risk groups Preschool/School aged children; Women of childbearing age (including pregnant women in the second and third trimesters and breastfeeding women). Recommendation Periodic treatment with anthelmintic (deworming) drugs Prevalence over 20%- treatment once a year Prevalence over 50%-treatment twice a year

Romana's sign

Associated with the acute stage of Chagas' disease. It is unilateral painless periorbital/lymphoid swelling which occurs when the T. cruzi enters through the conjunctiva. Not to be confused with a chagoma (A chagoma is an inflammatory nodule at the bite site of the reduviid bug)

Cystoisospora belli Life cycle

At the time of excretion in stool, the oocyst is immature and usually contains just one sporoblast (sometimes, two) . During further maturation after excretion, the sporoblast divides into two (the oocyst now contains two sporoblasts); the sporoblasts secrete a cyst wall, thus becoming sporocysts; and the sporocysts divide twice, resulting in four sporozoites per each of two sporocysts . Infection occurs by ingestion of mature (fully sporulated) oocysts: the sporocysts excyst in the small intestine and release their sporozoites, which invade the epithelial cells and initiate schizogony (asexual reproduction). Upon rupture of the schizonts, merozoites are released, which invade epithelial cells and continue the cycle of asexual multiplication. Trophozoites develop into schizonts, which contain multiple merozoites. After a minimum of one week, the sexual stage begins, with the development of male and female gametocytes . Fertilization results in the development of oocysts, which are excreted in the stool

Pathogenesis of Ticks

Attach at any point at the body but favor-scalp, hairline, ears, axillae, groin; Take blood meal Minor consequence-generally limited to small erythematous papule Serious consequence: Releases through saliva a neurotoxin that blocks acetylcholine release at the neuromuscular junction (action similar to botulinum toxin), requires at least 4 days contact Ascending flaccid paralysis (from legs to head within hours) resembling Gullain-Barre syndrome: Early signs-ataxia, symmetrical paralysis, fever Respiratory failure and death Recovery can occur within 24 hours of removal of tick

Pathogenesis of Fasciolopsis buski

Attachment of flukes in the small intestine produces inflammation, ulceration and hemorrhage, obstruction, abdominal discomfort, mal-absorption, diarrhea

Pathogenesis of Chiggers

Attack the areas where clothing is tight Saliva injected into the skin at the time of mite attachment produces and intense pruritic erythematous marks- may persist for wks. Mite larva visible at the center of the reddened swollen area Severe irritation may cause fever and sleep disturbance Excoriation and secondary bacterial infection can occur The stylostome is a funnel or channel-like structure formed by trombiculid mites. The formation is not caused by the mouthparts of the mites, because these mites do not have needle-like mouthparts, but have chelicerae, which only pierce the skin. The tube is formed by the digestive enzymes in the saliva, which is the same salivary secretions that break down cells that is causing the surrounding tissue to harden. As the mite feeds longer, the saliva seeps farther down, and digesting more tissue, therefore causes the stylostome to penetrate to lower layers of skin.

Bacterial Growth

Bacteria grow in size and number. Growth in number - population growth Population size increases by cell division They divide by binary fission A single cell divides to give two identical daughter cells The number of cells (population size) = 2n (n = generation number) This is exponential growth The doubling time - generation time varies Escherichia coli - 20 min Mycobacterium tuberculosis - 24 hrs

Intrinsic Resistance

Bacteria lacking the target - e.g, lack of peptidoglycan. Cell wall less: Mycoplasma, Ureaplasma Cell wall without typical peptidoglycan: Chlamydia, Chlamydophila,Orientia, Ehrlichia and Anaplasma, Rickettsia The antimicrobial cannot enter the bacterium eg. Gram negative bacteria due to the outer membrane; Acid fast bacteria due to mycolic acid

Naturally Cell Wall-Less

Bacteria that do not produce peptidoglycan, but have unusual form of cell wall. These are Chlamydia, Chlamydophila, Ehrlichia, Orientia and Anaplasma. Are resistant to antimicrobials which target peptidoglycan synthesis Components: (Picture) No peptidoglycan present Assume a variety of shapes Sterols within a phospholipid Bi-layer membrane; Maintain fluidity Cannot be stained using the Gram stain procedure Resistant to antibiotics that target cell wall Examples of Cell Wall-Less Bacteria: Mycoplasma spp. Ureaplasma spp.

Diagnosis of Taenia saginata

By detection of eggs/proglottids or entire worm in the stool (eggs similar to that of T. solium) Differentiation between T. solium & T. saginata based on their scolices and gravid segments Treatment: praziquantel, niclosamide Control & Prevention; proper cooking of beef, washing kitchen utensils after cutting meat.

Diagnosis of Clonorchis sinensis

By identification of eggs in the stool Egg- oval shaped, bile stained a convex operculum, that rests on visible "shoulders," at the smaller end of the egg. a small knob or hook-like structure at the opposite (larger, abopercular) end, Approx. 30 ×15µm

Live attenuated influenza vaccine

Called FluMist (in the form of nasal spray), uses a temperature-sensitive mutant that can be reassorted with any new virulent influenza strain that appears. The reassorted virus will have the genes for the internal proteins from the attenuated virus (and hence will be attenuated) but will display the surface proteins of the new virulent antigenic variant.

Toll like receptors

Can directly activate NK cells in case of viral infection

Dilution test

Can measure MIC: Minimal inhibitory concentration MBC: Minimal bactericidal concentration Can be automated - results in few hrs Series of dilutions of the drug in broth media - inoculate same number of bacteria in every tube and determine the lowest concentration of drug that inhibits the growth of a particular bacteria, Minimum inhibitory concentration (MIC) = eg (below) 3.1 g/mL Does not mean this kills the bacterial isolate, only inhibits Minimal bactericidal Concentration (MBC) = 6.2 µg/ml that kills at least 99% of the bacteria For some infections -e.g, endocarditis- it may be necessary to determine amount of antibiotic that kills the bacteria, and also immunocompromised patients should be given a dose that would kill -the bacteria Bactericidal drugs usually have an MBC equal or very similar to the MIC, whereas bacteriostatic drugs usually have an MBC significantly higher than the MIC (Ref: Levinson)

Pathogenesis of Hymenolepis nana

Clinical Disease: No symptoms with few worms Heavy infections: diarrhea, abdominal pain, headache, loss of appetite, itchy sensation

Interference

Capsule: antiphagocytic Biofilm: prevent complement and antibodies Avoid killing: Inhibition of phagosome function or escape into the cytoplasm Killing of phagocytic cell by producing toxins Avoiding Ig mediated opsonization; bind Fc of IgG -Protein A of Staphylococcus aureus and -M protein of Streptococcus pyogenes Cleavage of antibodies/complement IgA proteases, C5a proteases

Wuchereria bancrofti and Brugia malayi

Cause Elephantiasis Epidemiology: tropical, subtropical Transmitted by mosquito, (feeds in night) For W. bancrofti-No animal reservoir For. B. malayi: animal reservoirs (Cats and Monkeys)

Opportunistic pathogens

Cause disease in immun-ocompromised individuals or when normal flora enter body site other than normal site or overgrowth Microbes with small IDs have greater virulence. True pathogens (primary pathogens): cause disease in immuno-competent individuals

Pathogenesis of Trichuriasis

Clinical disease: Mostly asymptomatic Heavier infections: chronic profuse mucus and bloody diarrhea with abdominal pain and edematous PROLAPSED rectum. may result in appendicitis, malnutrition, anemia, weight loss, growth retardation and sometimes death.

Direct Light Microscopic Examination

Clinical sample: sputum, lung biopsy, skin scraping Wet mount or stained smears -Wet mount: KOH: Treat the sample with 10% KOH to clear debris; Stains -Gram stain: in suspected yeast infection, Candida may stain as G +. -Indian ink (negative staining): for detection of capsulated fungus -Calcofluor white stain: is fluorescent and binds to chitin -Other stains: Periodic acid Schiff (PAS), Gomori methanamine silver (GMS), Giemsa, Hematoxylin and eosin, immunofluorescent staining Determine Morphology: yeast or mold; hyphal structure, asexual spores

Botulinum toxin

Clostridium botulinum toxin blocks/inactivates SNARE proteins needed for acetylcholine release causing flaccid paralysis

A-B toxins neurotoxins

Clostridium botulinum: toxin inactivates proteins [SNARE proteins (synaptobrevin and syntaxin required for the release of acetylcholine] Synaptobrevins are small integral membrane proteins of secretory vesicles Tetanus toxin affects anterior horn cells of the spinal cord and brain stem. Cleaves synaptobrevin and blocks release of inhibitory transmitter from inhibitory terminals produces hyperflexia and spasms of skeletal muscles.

Tetanospasmin

Clostridium tetani: Blocks release of neuro inhibitor (glycine and gamma amino butyric acid) causing spastic paralysis--tetanus

Satellite/defective viruses

Composed of protein and nucleic acid Mutation or deletion of part of their genome makes dependent on other viruses for replication Adeno-associated virus - replicates only in cells infected with adenovirus Delta agent - naked strand of RNA expressed only in the presence of hepatitis B virus

Peptidoglycan Monomer

Composed of: NAM: N-acetylmuramic acid NAG: N-acetylglucosamine * L-lysine could be replaced by another amino acid; D-aminopimelic acid (unique to bacteria) Unique to bacteria are NAM D forms of aa and D-aminopimelic acid Lysozyme: breaks the glycosyl bond - the bond that joins the two sugars Synthesized in the cytosol of the bacterium where they attach to a membrane carrier molecule called bactoprenol

Transfer of Fertility factor

Conjugation occurs turning an F- cell into an F+ cell The F factor must be completely transferred to ensure a copy of the tra operon (transfer operon) present. The tra operon drives the conjugation process Maintaining the plasmid in the cytoplasm is energy requiring. If there is no external pressure to maintain the plasmid, it may be lost over time = Curing

Significance of Transposition

Consequence of integration: Disruption of normal gene sequence Insertion of new genetic information Can carry several genes (Pathogenicity Islands-several genes under the control of a single promoter)-Gene products include toxins, adhesins, antibiotic resistance, etc

Mannitol Salt Agar

Contains a high concentration (~7.5%-10%) of salt (NaCl). It is also a differential medium for mannitol-fermenting staphylococci, containing carbohydrate mannitol and the pH indicator phenol red for detecting acid produced by mannitol-fermenting staphylococci. Selective - high osmotic pressure & % NaCl Differential - mannitol fermentation

Regulation of Gene Expression

Coordinated gene expression may be obtained by I. Operons: Clusters of co-regulated genes: with a promoter, operator and structural genes Operons could be Inducible or Repressible II. Sigma factor: a protein for initiation of RNA synthesis III. Quorum sensing: gene expression depends on population size Most metabolite regulatory mechanisms involve control of transcription of the gene into messenger RNA, rather than control of translation of the messenger RNA In order to adapt quickly and effectively to changes, bacteria have developed mechanisms to coordinate and regulate the expression of multicomponent genes. Quorum sensing is the regulation of gene expression in response to fluctuations in cell-population density.

Pure Culture

Culture with only one type of microbe. Pure culture techniques : several Streak plate: most commonly used

Drugs that inhibit cell wall synthesis

Cycloserine: an analogue to D-alanine: inhibits peptidoglycan synthesis Isoniazid (INH); prodrug; inhibits mycolic acid synthesis Ethionamide: derivative of INH, inhibits mycolic acid synthesis Pyrazinamide: prodrug; inhibits mycolic acid synthesis Ethambutol: Interferes with synthesis of arabinogalactan (part of the cell wall of acid fast bacteria), bacteriostatic All above drugs are used in the treatment of mycobacterial infections: (acid fast bacteria) First line essential: Rifampin, Isoniazid, Pyrazinamide, Ethambutol First line supplemental: Streptomycin, Rifabutin, Rifapentine Second line: Quinolones, Amikacin, Kanamycin, Capreomycin, Ethionamide, Para-aminosalicylic acid, cycloserine

Giardia lamblia: life cycle

Cysts are resistant forms and are responsible for transmission of giardiasis. Both cysts and trophozoites can be found in the feces (diagnostic stages) . The cysts are hardy and can survive several months in cold water. Infection occurs by the ingestion of cysts in contaminated water, food, or by the fecal-oral route (hands or fomites) . In the small intestine, excystation releases trophozoites (each cyst produces two trophozoites). Trophozoites multiply by longitudinal binary fission, remaining in the lumen of the proximal small bowel where they can be free or attached to the mucosa by a ventral sucking disk. Encystation occurs as the parasites transit toward the colon. The cyst is the stage found most commonly in nondiarrheal feces . Because the cysts are infectious when passed in the stool or shortly afterward, person-to-person transmission is possible. While animals are infected with Giardia, their importance as a reservoir is unclear.

Balantidium coli: life cycle

Cysts are the parasite stage responsible for transmission of balantidiasis . The host most often acquires the cyst through ingestion of contaminated food or water . Following ingestion, excystation occurs in the small intestine, and the trophozoites colonize the large intestine . The trophozoites reside in the lumen of the large intestine of humans and animals, where they replicate by binary fission. Trophozoites undergo encystation to produce infective cysts. Some trophozoites invade the wall of the colon and multiply. Some return to the lumen and disintegrate. Mature cysts are passed with feces.

Membrane Disrupting Toxins

Cytolysins /cytolytic toxins Promote leakage of water and ions, disrupting cell function or cell lysis Two actions: 1. Pore (channel) former Eg, Streptolysin O produced by Streptococcus pyogenes 2. Destruction of phospholipid bilayer Eg. lecithinase (alpha toxin) produced by Clostridium perfringens (gas gangrene) Some are known Hemolysins, leukocidins Some are known as RTX or CDC pore formers RTX - because they have repeats of amino acid sequence CDC - cholesterol dependent cytolysins

Lab Diagnosis of Hymenolepis nana

Demonstration in stool of characteristic egg with six-hooked embryo and polar filaments

Immunofluorecent staining of cell culture

DEAFF: detection of early antigen fluorescent foci Detection o viral antigens in cell culture Detection of early proteins (expressed at the early stage of viral replication) by monoclonal antibodies tagged with fluorescent dye This is a method used for the early diagnosis of CMV infection. In immunocompromised patients, The specimen is inoculated into cell culture which is examined 24 hours later by immunofluorescence for expressed CMV encoded early proteins. The monoclonal antibodies must be able to cover most, if not all strains of CMV.

Virulence

Degree of pathogenicity; measured by (ID50) or (LD50) Infectious dose (ID50) number of a pathogen enough to cause disease Lethal dose (LD50): number of a pathogen enough to kill a host

Diagnosis and Treatment of lice

Demonstration of adult lice and eggs (nits) Treatment: Permethrin: treatment of choice Gamma benzene hexachloride (lindane) lotion Permethrin-both pediculicidal (kils adult) as well as ovicidal Prevention: Education and practice of hygiene Not sharing articles/clothing Shaving the hair of affected areas Treating brushes, combs and bedding with pediculicide

Diagnosis of Trichomonas vaginalis

Demonstration of characteristic trophozoite in vaginal and urethral discharge; (unstained smears or Giemsa, papanicolaou stained smear) On Microscopy of wet preparation, T. vaginalis, which is larger than Polymorphonuclear leukocytes but smaller than an epithelial cell, it is recognized by its usually rapidly moving flagella, the rippling movement of undulating membrane and the jerky movement of the organism.

Diagnosis and treatment of chiggers

Demonstration of chiggers in skin scrapings Treatment: Antipruritics, Antihistaminics and Steroids Prevention and Control- Person going to chigger infested areas-insect repellents (eg.DEET)

Diagnosis of Balantidium coli

Demonstration of cyst and trophozoite in feces

Diagnosis of Giardia lamblia

Demonstration of cyst or trophozoites Several stool samples may be necessary String test/ Entero test Usually a stool sample is tested first. A string test is done if the stool sample is negative. String test: a string with a weighted gelatin capsule is swallowed. Four hours later, it is pulled back out. Any bile, blood, or mucus (from small intestine) attached to the string is examined under the microscope for cells and parasites or parasite eggs.

Laboratory Diagnosis of Cyclospora cayetanensis

Demonstration of oocysts by Modified Ziehl-Neelsen (acid-fast) staining of formol-ether concentrated stool samples The oocysts are variably acid-fast. Demonstration of autofluorescence: The oocysts are refractile spheres which exhibit blue autofluorescence under ultraviolet light. Molecular: PCR

Diagnosis of Naegleria fowleri

Demonstration of organism in sterile tissue or fluid (CSF, nasal discharge) Detection of trophozoite by: Wet mount: live motile trophozoites Staining: Giemsa-staining, H & E staining or Florescent staining PCR Culture in a plate covered in bacteria, at 420 C The amoebae can be grown in culture to increase the likelihood of detection

Diagnosis of Acanthamoeba castellani

Demonstration of parasite in corneal scraping/CSF/biopsy from Sinus (H&E stain) Culture: Xenic and axenic culture Treatment: miltefosine Prevention & Control Proper care of eye lenses Steps to prevent GAE: unclear

Diagnosis of Diphyllobothrium latum

Demonstration of proglottids & bile stained operculated eggs (with knob) in stool Operculum - lid/covering opened at maturity

Diagnosis of T. Brucei

Demonstration of trypomastigotes in body fluids From primary lesion, blood, CSF

Heavy metals

Denature proteins Silver nitrate: used to prevent eye infection in new born babies from gonococcal infections

Bacterial Cell Group Arrangement

Depends on the line of consecutive cell divisions and the tendency of daughter cells to remain attached to each other after cell division

Rifamycin

Derivatives: Rifamycin, Rifampin/Rifampicin, Rifabutin Mechanism of Action Inhibits DNA-dependent RNA polymerase - prevents RNA synthesis Pharmacology Bactericidal, Broad spectrum Mycobacterium tuberculosis, Gram positives, some Gram negatives (but not all) Mechanism of Resistance Alteration of RNA polymerase

Lincosamides

Derivatives: Clindamycin (mainly), Lincomycin Mechanism: bind to the 23S rRNA of the 50S ribosomes and cause premature dissociation of the peptidyl-tRNA Bacteriostatic: effective against Gram positive cocci and against Gram -ve anaerobes. Inactive against Gram negative aerobes Resistance: methylation of the 23S rRNA Side effects: suppression of normal flora of GIT increases the risk of Clostridium difficile colitis

Carbapenems

Derivatives: Imipenem, meropenem Mechanism of action: Inh. cell wall synthesis Pharmacology: Bactericidal, broadest spectrum compared to penicillins and cephalosporins, Effective - Gram negative and positives; and also strict anaerobes Active against most beta-lactamases producing organisms including Extended spectrum beta-lactamase producers 'Drugs of last resort' against bacteria resistant to multiple antibiotics Resistance: Enzymatic inactivation by Carbapenemase (a form of beta-lactamases); resistant Gram negative rods on the increase. Klebsiella pneumoniae and Escherichia coli Strains are Multidrug resistant Outbreak with CRE in US in 2015

Quinolones and fluoroquinolones

Derivatives: several Nalidixic acid - original drug not in use any more, resistance high Ciprofloxacin, Ofloxacin, Norfloxacin, Mechanism of Action Inhibits bacterial DNA topoisomerases II (gyrase) and topoisomerases IV. Topoisomerases are required for DNA replication, recombination and repair. Fluoroquinolones are derivatives of the Quinolones because they have fluorine . Not recommended for children and pregnant women, affects bone and cartilage. Pharmacology: Bactericidal - broad spectrum Oral administration Mechanisms of Resistance Alteration of target site: bacterial DNA gyrase/topoisomerases Decreased permeability: Alteration of outer membrane proteins Export through efflux pumps

Genotype test

Detect resistant gene: ex. Van A and Van B genes for Vancomycin DNA hybridization Sequencing PCR (Amplification) Rapid, detect presence of the resistant gene but it may not mean expression of the gene

Diagnosis of Enterobiasis

Detection of adult worms and eggs by: Peri-anal swab-method of choice Scotch tape Occasionally, stool specimens Eggs are thin walled and assymmetrical

Haemadsorption

Detection of viral peplomers (hemagglutinins on infected cells) Occurs as a consequence of the insertion of viral peplomers (that have the ability to bind to RBC) into the surface of infected cells, chicken RBCs can now bind to these peplomers on the surface of the infected cells phenomenon is particularly useful in detecting infection by viruses that cause little cytopathic effect. useful for enveloped viruses that express hemagglutinins (surface gp - binds to RBC)

Electron Microscopy

Detection of virus in specimens Study of Size, Morphology Detection and identification of virus can be enhanced by using virus specific ab (Ab agglutinate virus) or by immunofluorescence

Guaiac test

Detects the presence of fecal occult blood (blood invisible in the feces). Occult blood in the stool indicates gastro intestinal bleeding that may be because of Helminth infestation (e.g, hookworm infection), colon cancer, polyps (abnormal growths) in the colon/rectum etc Principle of the test: When the hydrogen peroxide is dripped on to the guaiac paper (containing alpha-guaiaconic acid), it oxidizes the alpha-guaiaconic acid to a blue colored quinone. Normally, when no blood and no peroxidases or catalases from vegetables are present, this oxidation occurs very slowly. Heme, a component of hemoglobin if present in the sample, catalyzes this reaction, giving a result in about two seconds. A quick and intense blue color change of the film indicates positive test.

Diagnosis and Treatment of myiasis

Diagnosis: Generally by clinical findings Laboratory needed only for confirmation of larvae Treatment: Surgical removal: most common mode of treatment Manual extraction of larvae Petroleum jelly: Anoxia induces larvae to migrate to surface Prevention: Limiting exposure to flies Wearing long sleeved clothes, mosquito netting, insect repellants

Amoebic Liver Abscess

Diagnostic aspiration: Aspirated pus examined for the presence of trophozoites (Not cysts!!!!) Or, Liver biopsy Along with examination of stool, Serological tests Radiological examination PCR and DNA probe assay

Acid Fast Staining

Differential Staining Common method is Ziehl-Neelsen (Z-N) stain - used to stain Acid fast bacteria (AFB) Requires heating of a primary stain, decolorizing with an acid/acid-alcohol solution, and then pouring a secondary dye.

Gram Staining

Differential Staining A process by which components of bacterial cell walls are bound to Gram's stain. Depending on the amount of peptidoglycan in their cell walls, bacteria stain differently and are classified as Gram-negative or Gram-positive.

Treatment of Clonorchis sinensis

Drug of choice- praziquantel Prevention & Control: Avoid eating raw, pickled, smoked fresh water fish; Education regarding mode of transmission of parasite and proper disposal of human feces

Flies

Disease: Myiasis (caused by larvae/maggots): Transmission: Deposition of eggs which hatches to larvae Directly on wounds/abrasions or nostrils, conjunctiva, lips and even on unbroken skin Via mosquitos (eg. Bot fly) Specific myiasis: by flies which require a host for larval development eg. Human botfly: Dermatobia hominis Epidemiology: Worldwide, Tropical areas Infects humans as well as many animals

Treatment of Loiasis

Drug of choice-Di-ethylcarbamazine (DEC)-effective for adults and microfilariae Corticosteroid may be added: to control the severe allergic reactions resulting from the destruction of the parasites Surgical removal after application of 10% cocaine Prevention and Control Health education Protection from fly bites using screening, appropriate clothing and insect repellents Early treatment of cases

Treatment of Fasciolopsis buski

Drug of choice-Praziquantel Prevention and Control: Education on safe consumption of aquatic vegetations, Chestnuts Use of molluscacides to control snails, Control of reservoir hosts, Early treatment of cases

Treatment of Schistosomiasis

Drug of choice-Praziquantel Prevention: Destruction of snail habitat: Clearing water plants where the snail lives (they breed on vegetables along the sides of freshwater bodies) Elimination of snails: chemicals Avoid swimming in endemic areas

Treatment of Ancylostoma caninum & braziliense

Drug of choice-albendazole Prevention and control Health education to pet owners to treat for worm infections in their pets Hygiene and sanitation Wearing shoes and sandals in endemic areas

Treatment of Hookworm infection

Drug of choice-albendazole/ mebendazole Prevention: Education Sanitation Not walking barefoot in areas where hookworm is common; wearing shoes By not defecating outdoors and by effective sewage disposal systems.

Treatment of Trichuriasis

Drug of choice-albendazole/mebendazole Prevention: education, good personal hygiene

Treatment of Diphyllobothrium latum

Drug of choice-niclosamide a phenol, has selective activity against intestinal tapeworms. It acts by uncoupling oxidative phosphorylation in mitochondria, resulting in a loss of helminth ATP, that causes immobilization of the parasite and expel it with the feces. Prevention: avoiding insufficiently cooked fish; proper disposal of human feces

Treatment of Paragonimus westermani

Drug of choice-triclabendazole (Benzimidazole): broad spectrum anthelmintic agent, acts by: 1] inhibition of fumarate-reductase of the parasite 2] inhibition of glucose transport, resulting in glycogen depletion, cessation of ATP formation and paralysis or death and 3] disruption of microtubular function and elimination of their motility Prevention & Control: Avoiding eating raw, pickled, smoked crabs and crayfish; Education; Proper disposal of human feces

Treatment of Strongyloides stercoralis

Drug of choice: Ivermectin Interacts with chloride channel resulting in hyperpolarization, paralysis and death of the parasite Alternative: Albindazole/mebendazole Prevention and Control Similar to Hookworm infection

Treatment of Trichomonas vaginalis

Drug of choice: Metronidazole Prevention and control Safe sexual practices Personal hygiene Avoidance of sharing toilet articles

T. brucei (African Trypanosoma): Life cycle

During a blood meal on the mammalian host, an infected tsetse fly (genus Glossina) injects metacyclic trypomastigotes into skin tissue. The parasites enter the lymphatic system and pass into the bloodstream. Inside the host, they transform into bloodstream trypomastigotes , are carried to other sites throughout the body, reach other blood fluids (e.g., lymph, spinal fluid), and continue the replication by binary fission . The entire life cycle of African Trypanosomes is represented by extracellular stages. The tsetse fly becomes infected with bloodstream trypomastigotes when taking a blood meal on an infected mammalian host. In the fly's midgut, the parasites transform into procyclic trypomastigotes, multiply by binary fission , leave the midgut, and transform into epimastigotes . The epimastigotes reach the fly's salivary glands and continue multiplication by binary fission, producing metacyclic trypomastigotes . The cycle in the fly takes approximately 3 weeks. Humans are the main reservoir for Trypanosoma brucei gambiense, but this species can also be found in animals. Wild game animals are the main reservoir of T. b. rhodesiense.

Onchocerca volvulus life cycle

During a blood meal, an infected blackfly (genus Simulium) introduces third-stage filarial larvae onto the skin of the human host, where they penetrate into the bite wound . In subcutaneous tissues the larvae develop into adult filariae, which commonly reside in nodules in subcutaneous connective tissues . Adults can live in the nodules for approximately 15 years. Some nodules may contain numerous male and female worms. Females measure 33 to 50 cm in length and 270 to 400 μm in diameter, while males measure 19 to 42 mm by 130 to 210 μm. In the subcutaneous nodules, the female worms are capable of producing microfilariae for approximately 9 years. The microfilariae, measuring 220 to 360 µm by 5 to 9 µm and unsheathed, have a life span that may reach 2 years. They are occasionally found in peripheral blood, urine, and sputum but are typically found in the skin and in the lymphatics of connective tissues . A blackfly ingests the microfilariae during a blood meal . After ingestion, the microfilariae migrate from the blackfly's midgut through the hemocoel to the thoracic muscles . There the microfilariae develop into first-stage larvae and subsequently into third-stage infective larvae . The third-stage infective larvae migrate to the blackfly's proboscis and can infect another human when the fly takes a blood meal.

W. bancrofti and B. malayi Life Cycle

During a blood meal, an infected mosquito introduces third-stage filarial larvae onto the skin of the human host, where they penetrate into the bite wound. They develop in adults that commonly reside in the lymphatics . The female worms of W. bancrofti measure 80 to 100 mm in length and 0.24 to 0.30 mm in diameter, while the males measure about 40 mm by .1 mm (The adult worms of B. Malayi are smaller. Female worms measure 43 to 55 mm in length by 130 to 170 μm in width, and males measure 13 to 23 mm in length by 70 to 80 μm in width). Adults of W. bancrofti produce microfilariae measuring 244 to 296 μm by 7.5 to 10 μm (microfilariae of B. malayi, measuring 177 to 230 μm in length and 5 to 7 μm in width), which are sheathed and have nocturnal periodicity. The microfilariae migrate into lymph and blood channels moving actively through lymph and blood. A mosquito ingests the microfilariae during a blood meal . After ingestion, the microfilariae lose their sheaths and some of them work their way through the wall of the proventriculus and cardiac portion of the mosquito's midgut and reach the thoracic muscles . There the microfilariae develop into first-stage larvae and subsequently into third-stage infective larvae . The third-stage infective larvae migrate through the hemocoel to the mosquito's proboscis and can infect another human when the mosquito takes a blood meal .

ADCC (antibody-dependent cell-mediated cytotoxicity)

During replication of a virus some of the viral proteins are expressed on the cell surface membrane of the infected cell. Antibodies can then bind to these viral proteins. Next, the NK cells which have Fc Receptors will bind to that antibody, inducing the NK cell to release proteins such as perforin and proteases known as granzymes, which causes the lysis of the infected cell to hinder the spread of the virus

Malarial Infection of RBC

During the erythrocytic stage of the parasite's life cycle, it uses intracellular hemoglobin as a food source. The protein is broken down into peptides, and the heme group is released and detoxified in the form of hemozoin Maurer clefts/dots: finely granular precipitates or irregular cytoplasmic particles that usually occur diffusely in red blood cells infectedwith the trophozoites of Plasmodium falciparum. They are membrane-limited vacuoles or sack-like structures in the cytosol of the erythrocyte, formed early after invasion by the parasite, visible as blue dots in Giemsa-stained blood smears. Their origin and functions remain still unclear.

Maturation

During this time, viral coded envelope glycoproteins are inserted in the host cell's membranes by the Golgi apparatus. Viruses that will be released by exocytosis obtain their envelopes by budding from the nuclear membrane, the endoplasmic reticulum, and/or from the Golgi complex. These enveloped viruses are then packaged in exocytic vesicles for release from the host cell by exocytosis. Matrix proteins for negative stranded RNA viruses line and promote the adhesion of nucleocapsid with glycoprotein-modified membrane. As more interaction occur, the membrane surrounds the nucleocapsid, and the virus buds from the membrane.

Hymenolepis nana

Dwarf tapeworm Epidemiology: worldwide, most often seen in Children (with poor hygiene)/day care centers Most common tapeworm infection in US. Infects humans, rodents and arthropods. Intermediate host not essential for human infection (but can pass through intermediate host as well) Transmission: fecal-oral, autoinfection, ingestion of arthropods (e.g beetles) in contaminated grain/flour Morphology Embryonated eggs (contain embryophore with 3 pairs of hooklets & polar filaments) Larva: Cysticercoid (attach on small intestine) Adult worm (2-4 cm in length, thread like)

Antibiotic sensitivity test

E.g Optochin sensitivity for alpha hemolytic Streptococcus spp.

Lice life cycle

Egg, nymph, and adult (CDC) Eggs: Nits are head lice eggs. They are hard to see and are often confused for dandruff or hair spray droplets. Nits are laid by the adult female and are cemented at the base of the hair shaft nearest the scalp . They are 0.8 mm by 0.3 mm, oval and usually yellow to white. Nits take about 1 week to hatch (range 6 to 9 days). Viable eggs are usually located within 6 mm of the scalp. Nymphs: The egg hatches to release a nymph . The nit shell then becomes a more visible dull yellow and remains attached to the hair shaft. The nymph looks like an adult head louse, but is about the size of a pinhead. Nymphs mature after three molts and become adults about 7 days after hatching. Adults: The adult louse is about the size of a sesame seed, has 6 legs (each with claws), and is tan to grayish-white. In persons with dark hair, the adult louse will appear darker. Females are usually larger than males and can lay up to 8 nits per day. Adult lice can live up to 30 days on a person's head. To live, adult lice need to feed on blood several times daily. Without blood meals, the louse will die within 1 to 2 days off the host

Paragonimus westermani life cycle

Eggs excreted in the sputum and sometimes in the stool Eggs are excreted unembryonated in the sputum, or alternately they are swallowed and passed with stool. In the external environment, the eggs become embryonated , and miracidia hatch and seek the first intermediate host, a snail, and penetrate its soft tissues . Miracidia go through several developmental stages inside the snail : sporocysts , rediae , with the latter giving rise to many cercariae , which emerge from the snail. The cercariae invade the second intermediate host, a crustacean such as a crab or crayfish, where they encyst and become metacercariae. This is the infective stage for the mammalian host . Human infection with P. westermani occurs by eating inadequately cooked or pickled crab or crayfish that harbor metacercariae of the parasite. The metacercariae excyst in the duodenum , penetrate through the intestinal wall into the peritoneal cavity, then through the abdominal wall and diaphragm into the lungs, where they become encapsulated and develop into adults (7.5 to 12 mm by 4 to 6 mm). The worms can also reach other organs and tissues, such as the brain and striated muscles, respectively. However, when this takes place, completion of the life cycles is not achieved, because the eggs laid cannot exit these sites. Time from infection to oviposition is 65 to 90 days. Infections may persist for 20 years in humans. Animals such as pigs, dogs, and a variety of feline species can also harbor P. westermani. Crustaceans like crabs, cray fish contain larva (metacercaria)- ingestion of which lead to human infection.

LPS (lipopolysaccharide)

Endotoxin Lipid A component of LPS of the cell wall of Gram-negatives Released after the bacteria die Activates several aspects of the immune system including the coagulation system. Acts as PAMP : activates macrophages, PMN, mast cells, endoth. cells, platelets Activates complement: alternative pathway B cell polyclonal activation Effects Low concentrations signal inflammation necessary for clearing infection High concentrations: Endotoxic shock, " SIRS"- systemic inflam. response syndrome Symptoms: Fever, Hypotension and DIC (disseminated intravascular coagulation) , inflammation, multi-organ failure, death

Bacterial Toxins

Endotoxins and Exotoxins Note: Teichoic and lipoteichoic acid, peptidoglycan of Gram positive can cause fever, acute phase response similar to that caused by Endotoxin

Viral Structure

Envelope: lipid bilayer from host cell and viral glycoproteins Peplomers/Spikes: viral glycoprotein, binding to host cell Matrix protein- mediate attachment of capsid with the envelope Packaged enzymes: facilitate initial viral replication (polymerases, proteases). May be located inside the nucleocapsid or in the space between the capsid and envelope (tegument) Other proteins: structural proteins: part of virion non-structural proteins: not in virion, involved in early events of replication

DNA Replication in Prokaryotic Cells

Enzymes & proteins required for bacterial replication are similar to those found in eukaryotic cells but different enough to be targets for specific antibiotics Replication requires uncoiling of supercoiled DNA. Antibiotics of class flouroquinolones bind to DNA gyrase (topoisomerase II) and inhibit uncoiling of supercoiling.

Transglycosylase

Enzymes facilitate formation of glycosidic bond to link peptidoglycan monomers

Loeffler's syndrome

Eosinophilic pneumonia caused by the parasites Ascaris lumbricoides, Strongyloides stercoralis and the hookworms (Ancylostoma duodenale and Necator americanus). Although Löffler only described eosinophilic pneumonia in the context of infection, many authors give the term "Löffler's syndrome" to any form of acute onset pulmonary eosinophilia no matter what the underlying cause is.

Cyclospora cayetanensis

Epidemiology: Worldwide but common in tropical and subtropical regions; Also infects animals Travelers, indigenous persons living in developing countries and immuno- compromised (particularly, HIV infected) person Transmission: by ingestion of food/vegetables/fruits/water contaminated with sporulated oocyst, outbreaks in US since 1990s Biology: Single celled coccidian parasite, both sexual and asexual reproduction

Trypanosoma cruzi (Chagas Disease/ American trypanosomiasis)

Epidemiology: infects human, domestic cats, dogs, wild rats, raccoon and even armadillo and opossums Transmitted: by insect vector Reduviid bugs (Triatomine bugs/kissing bugs); across the placenta (congenital); and by blood transfusion/organ transplantation Geographic distribution: Rural areas of South and Central America: endemic Migrants in the USA, Europe, Australia, Japan Morphology: exists as a flagellate and non flagellate

Acanthamoeba castellani

Epidemiology: ubiquitous in nature; water bodies, warm climate, hot tub Transmission: by contaminated water/soil through damaged skin, corneal abrasion; inhalation Risk factors: improper contact lens care and contact with nonsterile water during wear. Rare disease; incidence in developed countries: approx. 1 to 33 cases per million contact lens wearers Morphology: free living Amoeba (Protozoan), exists in two stages, cysts and trophozoite

Balantidium coli

Epidemiology: world wide, mostly tropical and subtropical, rare in US - infects animals - Risk factors: working with animals (pigs farm) and immune-compromised status fecal-oral route Outbreak associated with contaminated water supplies with pig feces. Biology: ciliate - cyst and trophozoite Trophozoite-covered with cillia (aid in motility), funnel like mouth (cytostome), has 2 nuclei - macro and micro nuclei, 50-200× 40-70 µm Cyst: refractile wall, single nucleus, 40-60µm (diameter)

Cystoisospora belli (Formerly, Isospora belli)

Epidemiology: worldwide, healthy as well as immunocompromised patients, Transm. by ingestion of contaminated food or water Least common of 3 intestinal coccidian Biology: sporozoan (coccidian), both asexual (schizogony) and sexual (gametogony) reproduction The least common of all 3 intestinal coccidian (CDC)

Plasmids

Extra-chromosomal DNA, circular One or more in a cell, Can be lost or gained Replicate independent of the main chromosome Can integrate into the main chromosome (episome) Carries genes - for specialized function, but not essential for survival such as R-plasmid - antibiotic resistance gene

Pathogenesis of Trypanosomiasis

Extracellular - multiply in body fluids Programmed gene rearrangement (Antigenic variation)/ about 1000 gene varieties Lesion at the site of insect bite (Chancre) Gambian sleeping sickness (West ASS): IP-few days to weeks, can progress to chronic disease-fatal Early (hemolymphatic phage): Fever (intermittent/weekly), myalgia, arthralgia and lymphadenopathy (Posterior cervical lymphadenopathy-Winterbottom's sign), Rash Chronic (Neurologic phage): CNS involvement (usually after 1-2 year )-lethargy, daytime sleepiness with night sleep disturbance, tremors, meningoencephalitis, mental retardation, convulsions, hemiplegia, coma and death

Plasmids

Extrachromosomal genetic material (circular, DsDNA) Non essential genetic information May have more than one copy of a single plasmid

Transpeptidase

Facilitate formation of peptide cross-links between the amino acid layers of peptidoglycan to make the wall strong Inhibited by penicillins

Diagnosis and treatment of Ticks

Finding of a tick or a history of exposure + clinical features Treatment: Early removal of ticks Prevention and control: Wearing of protective clothing that cover extremities Application of insect repellents Inspection of people and pets for ticks after visits to tick infested areas

Maurer dots

Finely granular precipitates or irregular cytoplasmic particles that usuallyoccur diffusely in red blood cells infected with the trophozoites of Plasmodium falciparum. They are membrane-limited vacuoles or sack-like structures in the cytosol of the erythrocyte, formed early after invasion by the parasite, visible as blue dots in Giemsa-stained blood smears. Their origin and functions remain still unclear.

Diphyllobothrium latum

Fish tapeworm Epidemiology: worldwide, cool lake regions (Northern hemisphere/North America) Reservoirs hosts: multiple fish eating wild and domestic animals Intermediate hosts: Crustaceans and fish Transmission: Ingestion of raw or undercooked fresh water fish Morphology: Adult up to 25 m long (largest tapeworm infecting humans), larva and operculated egg (diagnostic stage)

Diphyllobothrium latum: life cycle

Fish tapeworm: crustaceans (also called copepods which includes Cyclops/ and Diaptomus spp) and fish are intermediate hosts Immature eggs are passed in feces . Under appropriate conditions, the eggs mature (approximately 18 to 20 days) and yield oncospheres which develop into a coracidia . After ingestion by a suitable freshwater crustacean (the copepod first intermediate host) the coracidia develop into procercoid larvae . Following ingestion of the copepod by a suitable second intermediate host, typically minnows and other small freshwater fish, the procercoid larvae are released from the crustacean and migrate into the fish flesh where they develop into a plerocercoid larvae (sparganum) . The plerocercoid larvae are the infective stage for humans. Because humans do not generally eat undercooked minnows and similar small freshwater fish, these do not represent an important source of infection. Nevertheless, these small second intermediate hosts can be eaten by larger predator species, e.g., trout, perch, walleyed pike . In this case, the sparganum can migrate to the musculature of the larger predator fish and humans can acquire the disease by eating these later intermediate infected host fish raw or undercooked . After ingestion of the infected fish, the plerocercoid develop into immature adults and then into mature adult tapeworms which will reside in the small intestine. The adults of D. latum attach to the intestinal mucosa by means of the two bilateral groves (bothria) of their scolex . The adults can reach more than 10 m in length, with more than 3,000 proglottids. Immature eggs are discharged from the proglottids (up to 1,000,000 eggs per day per worm) and are passed in the feces . Eggs appear in the feces 5 to 6 weeks after infection. In addition to humans, many other mammals can also serve as definitive hosts for D. latum.

Electron Microscope

Focuses a beam of electrons through the specimen or onto its surface TEM or SEM

Treatment of Toxocariasis and Baylisarcaris

For Toxocariasis Visceral: antiparasitic agents-albindazole or mebendazole Ocular- difficult to treat, measures to prevent further damage Antiparasitic agents for early infection; Corticosteroid For Baylisarcaris infection-No effective drugs; EXTREMELY FATAL Prevention and Control: Eradication of worms by the pet owners; Hygiene and sanitation; Proper disposal of pet's feces Discouraging keeping of raccoons as pets

Western blot

For detection of antiviral antibodies: The viral antigens are separated by electrophoresis, then transferred onto nitrocellulose membrane. The membrane is now reacted with the patient's serum containing the specific antiviral antibodies. The antibodies are now detected by secondary enzyme labeled antibody and substrate.

Flagella

For motility Gen. in rod shaped bacteria Flagellin proteins Variation in aa sequence - antigenic variation provides serologic classification Capable of being regenerated Number and position vary Generally found in many Gram negative bacteria. However, some of the Gram positive organisms like Vagococcus, two species of Enterococci (Enterococcus casseliflavus and E. gallinarum) have flagella

Pathogenesis of Echinococcosis granulosus

Form cyst (larvae) inside tissues - and grows - mechanical destruction & space occupying lesions Type I Hyp. rxn due to leakage of cyst contents/fluid- Anaphylaxis, shock and DEATH Daughter cysts also develop and escape to other organs - liver, lung, and brain Clinical Disease: Hydatid disease or hydatidosis Cyst grows and develops over 5 - 30 years. Pressure on the organs; scarring/loss of function - liver, lung, brain; Cysts can calcify over time, or may rupture & disseminate

Viral Nomenclature

Formal names: 1. Family names end in - viridae, e.g Orthomyxoviridae, Reoviridae 2. Genera names end in virus eg. Myxovirus, Reovirus Common names based on; 1. Target tissue—Rhinovirus, hepatitis virus 2. Geography—St. Louis encephalitis virus, Coxsackie virus 3. Shape—Coronavirus 4. Transmission--Arboviruses (arthropod borne) viruses

Fungal Sexual Reproduction

Formation of sexual spores (Teleomorph) 4 classes based on sexual spore formation Zygomycetes: have non septate hyphae, produce zygospores as sexual spores (They also produce sporangiospores as asexual spores) Ascomycetes: Include both yeasts and filamentous fungi (Septate), form ascospores (sexual spores) Basidiomycetes: Basidiospores on a basidium or base Deuteromycetes: Also called as Fungi imperfecti Provisional group whose sexual phase not identified Contains most fungi of medical importance

Sporangiospores

Formed in a sac called a sporangium, easily broken to free the spores

Laboratory Diagnosis of mycotic disease

Four approaches 1. Direct Light Microscopic Examination 2. Culture 3. Immunological tests/Serology 4. Molecular: eg, DNA probe tests

Koch's Postulates

Four criteria designed to establish a causative relationship between a microbe and a disease

Fungi as Infectious Agents

Fungi are widely distributed in nature Only few are associated with disease True/primary pathogens can cause disease in a healthy, immunocompetent host Opportunistic pathogens are fungi with weak/nonexistent virulence or invasiveness, cause disease in immunocompromised host Increase in incidence - 10% of all hospital acquired infections

Serotyping

Further Identification of isolates: detection of expressed antigens Slide agglutination: identify antigens present on the surface of specific microorganisms Use of Fluorescent dye tagged antibodies - DFA

Ethylene oxide

Gas Bactericidal even against spores Great penetrating power because it is a gas Alkylates protein and nucleic acid Used to sterilize bulky stuff such as bedding materials heat sensitive medical materials, like plastic gloves, syringes Highly toxic, so need of special chamber

Chigger mites

General Properties Chiggers (Larvae) have branched, feather like hairs Adult infest grass and bushes but their larvae (chiggers) attack humans and other vertebrates causing severe dermatitis The larvae are minute, barely visible, reddish dots attached to skin They use hooked mouth parts to ingest tissue fluids Epidemiology: Worldwide Medically important chiggers in US: larvae of Eutrombicula alfreddugesi and E. splendens Risk: Campers and picnickers

Trematodes

General Properties Small flat, leaf-like worms Measures in mm Have suckers for attachment The sexes of the parasites are not separate (monoecious). Except in one genus - Schistosoma All use freshwater snails as intermediate host

Adenovirus

Naked with Icosahedral capsid Capsomeres- hexons and pentons 12 vertices (with pentons) and 20 triangular faces (with hexons). Each face has no.of capsomers. Peplomers (fibers) - projections

Bedbugs

General properties Cimex lectularius: most common bedbug in US About 5 mm long, oval and brownish body, long folded proboscis Resides in mattresses and in the crevices of wooden beds in the day time Feed at night Pathogenesis and Clinical findings Bite in a linear fashion in the trunk, take blood meal Hypersensitivity reaction leading to a pruritic wheal Occasionally, sleeplessness in children and adults

Ectoparasites

Organisms found either on the skin or only in the superficial layer of skin Arthropods Ectoparasites causing human diseases-two categories: Insects (6 legged arthropods): Lice, Flies, Bed bugs Arachnids/chelicerates (8 legged arthropods): Mites, Ticks, Spiders

Types of Transduction

Generalized - transfer of any bacterial gene from the disrupted cell Specialized - transfer of specific genes after integration of phage into bacterial chromosome

Bacterial Genome

Genes on Chromosome and extra chromosomal element (if any) Chromosome Plasmid Prophage

Nucleoid

Genome not enclosed within a nuclear envelope Most bacterial chromosomes are single, circular, highly coiled and haploid Double stranded DNA No introns Ultrastructure: fine structure, especially within a cell, that can be seen only with the high magnification obtainable with an electron microscope. Has no histones (protein) in the chromosome

Surviving host defenses

To avoid immune attack by Interference: Camouflage: Antigenic Variation Coordinated expression of several genes (Pathogenicity islands) Camouflage: Disguise, concealment

Fasciolopsis buski

Giant Intestinal fluke Largest trematode: approx. 5 cm by 1.5cm Epidemiology: worldwide, common in China and other countries in south-east Asia; humans as definitive host and snail as intermediate host; pigs, dogs and rabbits as reservoir host Transmission: consumption of contaminated (with metacercaria) aquatic vegetations (eg. water chestnuts)

Pathogenesis of Giardia lamblia

Giardiasis Adhere to the wall of small intestine Malabsorption of food (fats and fat-soluble vitamins) Intestinal: non-bloody diarrhea: bulky, greasy stool/steatorrhea (Incubation Period: average of 10 days)

Gram Positive vs. Gram Negative Bacteria

Gram positive to take a positive stain and associated with respiratory and soft tissue infections Gram negative to obtain a negative stain and associated with genitourinary or gastrointestinal tract infections

Dracunculus medinensis

Guinea worm or fiery serpent Epidemiology: Tropical Africa Transmitted by consumption of water (from 'step wells') containing infected Copepod, Cyclops

Naegleria fowleri life cycle

Has 3 stages in its life cycle: , ameboid trophozoites , flagellates, and cysts. The only infective stage of the ameba is the ameboid trophozoite. Trophozoites are 10-35 µm long with a granular appearance and a single nucleus. The trophozoites replicate by binary division . Trophozoites infect humans or animals by penetrating the nasal tissue and migrating to the brain via the olfactory nerves causing primary amebic meningoencephalitis (PAM). Trophozoites can turn into a temporary, non-feeding, flagellated stage (10-16 µm in length) when stimulated by adverse environmental changes such as a reduced food source. They revert back to the trophozoite stage when favorable conditions return. Naegleria fowleri trophozoites are found in cerebrospinal fluid (CSF) and tissue, while flagellated forms are occasionally found in CSF. Cysts are not seen in brain tissue. If the environment is not conducive to continued feeding and growth (like cold temperatures, food becomes scarce) the ameba or flagellate will form a cyst. The cyst form is spherical and about 7-15 µm in diameter. It has a smooth, single-layered wall with a single nucleus. Cysts are environmentally resistant in order to increase the chances of survival until better environmental conditions occur.

Bacterial ribosomes

Has two units Differ from eukaryotic cell ribosome in size and chemical composition Bacterial ribosome size -70s with 50s and 30s subunits Eukaryotic cell ribosome size - 80s with 60s and 40s subunits Site for antibiotic action The Svedberg unit (S) offers a measure of particle size based on the rate of the sedimentation in the centrifugation

Medical Significance of Spores

Highly resistant to heat and chemicals Not killed by boiling, but are killed at 121 0C The spore coat is impermeable to many chemicals - Only few disinfectants can kill spores (sporicidal disinfectants) Can survive for many years in the environment - eg. soil Any thing that is contaminated in soil may contain spores tetanus and gas gangrene by spore forming bacteria Their use as sterilization controls: B. stearothermophilus: in autoclave B. subtilis and C. tetani: in hot air oven

Mode of Transmission

Human to human: Direct contact, No direct contact, Transplacental, Blood borne Non human to human: from soil source, water source, animal source, fomite source Major Routes of entry: 3I's + sexual + Mother to child Ingestion, Inhalation, Injection -deep wounds, arthropod , Sexual contact. In addition vertical transmission from mother to unborn fetus (transplacental) during delivery and after delivery via breast feeding.

Strongyloides stercoralis: Diagnosis

I. Larva (not eggs!!!) detection in stool or sputum Larva detection in stool by Baermann funnel gauze method II. Culture: charcoal culture or agar plate method; rarely used Tracks/furrows with motile larvae III. Serology: detection of antibodies; screening test or as an adjunct for diagnosis If the fecal sample is left for a day or more under tropical conditions, the larvae of hookworm will also have hatched out and eggs might no longer be evident.

Dracunculus medinensis Life Cycle

Humans become infected by drinking unfiltered water containing copepods (small crustaceans) which are infected with larvae of D. medinensis . Following ingestion, the copepods die and release the larvae, which penetrate the host stomach and intestinal wall and enter the abdominal cavity and retroperitoneal space . After maturation into adults and copulation, the male worms die and the females (length: 70 to 120 cm) migrate in the subcutaneous tissues towards the skin surface . Approximately one year after infection, the female worm induces a blister (due to release of toxic substances) on the skin, generally on the distal lower extremity, which ruptures. When this lesion comes into contact with water, a contact that the patient seeks to relieve the local discomfort, the female worm emerges and releases larvae . The larvae are ingested by a copepod and after two weeks (and two molts) have developed into infective larvae. Ingestion of the copepods closes the cycle .

Fasciolopsis buski life cycle

Humans ingest the encysted larval stage (metacercaria) through contaminated aquatic vegetations (eg. water chestnuts). The metacercaria gets released from the husk due to chewing action, swallowed and develop into immature flukes in the duodenum. The fluke attaches to the mucosa of small intestine with its suckers, develops into adult worms and undergoes self-fertilization. Eggs production usually starts 3 months after ingestion of metacercaria. The operculated eggs released in feces reach water and free swimming larval stage (miracidium) is liberated through operculum. The miracidium penetrates the soft tissue of snail with the help of certain lytic substances it produces. In the snail tissue, the miracidium develops through a series of stages. The final stage (cercaria) in the snail is a free swimming form that, after release from the snail, encysts on the aquatic vegetations, becoming the metacercaria or Infective stage

Ectoparasite Skin manifestation

Hypersensitivity reaction: Lice: pediculosis capitis/corporis/pubis Bedbugs: linear lesions Itch mite: Scabies/Mange/Itch Chigger mites: Severe dermatitis/trombiculosis) Myasis (Larval growth): Flies Necrotizing lesion: Necrotic arachnidism (Brown recluse spiders)

Fungal Reproduction

I. Asexual A. Vegetative reproduction By budding (in yeast) or fragmentation of hyphae B. Formation of asexual spores: Anamorph Several types: important in identification II. Sexual: Formation of sexual spores: Teleomorph Not used for identification, but for taxonomy

Fungal Morphology

I. Yeasts—oval, unicellular, reproduce by budding (blastoconidia) eg, Cryptococcus neoformans II. Yeast like: yeasts but form pseudohyphae (chain of elongated yeast cells, not true hyphae) during invasion of tissue eg, Candida albicans III. Mold form: thread-like tubular multicellular hyphae, colonies have cottony or velvety surface. Intertwining mass of hyphae is known as mycelium eg, Aspergillus spp. IV. Dimorphic: exist in 2 forms-yeast (at 37 0C) and mold (at 25 0C) interconversion between them influenced by temperature - Thermal dimorphism. Eg, Histoplasma capsulatum

DNA Viruses

I: ds DNA: replication is the same as for Eukaryotic DNA and can make mRNA from dsDNA, eg. Herpes virus use host DNAdep-DNApoly.(but varies) and DNA dependent RNA polymerase. _dsDNA viruses (e.g. Adenoviruses, Herpesviruses, Poxviruses) (Polyoma, papillomaviruses use host coded DNA polymerase whereas Adeno and Herpesviruses use viral coded DNA polymerases) II: ss DNA: replication passes through ds DNA then to mRNA, eg. parvovirus use a host DNAdep---DNApoly and DNA dependent RNA polymerase -ve strand or antisense ) DNA (e.g. Parvoviruses) VII: Partially ds DNA: replicate through RNA intermediate - Uses host DNA dep-RNA poly and code their own RNAdep-DNApoly. Eg. Hepatitis B (hepadnaviridae) VII: dsDNA-RT viruses (e.g. Hepadnaviruses i.e Hepatitis B virus)

Acquired Toxoplasma gondii

IP: 5-23 days A. Immunocompetent persons Cervical lymphadenopathy: most common Single or multiple, usually non tender Fever [usually <40°C] Headache, malaise, fatigue, myalgia, sore throat B. Immunocompromised patients: rapidly fatal if untreated -CNS: Principal opportunistic infection of the CNS in persons with AIDS meningoencephalitis, and mass lesions. -Lungs: Toxoplasma pneumonia (dyspnea, fever and non productive cough) -Heart: usually asymptomatic, but may progress to heart failure

Diagnosis of Loiasis

Identification of adult worms in the eyes Identification of microfilariae in blood smears taken between 10AM and 2PM (Day time) Serology

Diagnosis of Hookworm infection

Identification of eggs in stool - thin walled eggs with segmented ovum Differentiation between two hook worms-by study of their adult/larval morphologies and buccal capsules (hook like teeth or chitinous plates) Occult blood test (guaiac test): to detect presence of blood in stool

Diagnosis of Paragonimus westermani

Identification of operculated eggs in sputum and stool; x-ray

Fasciola hepatica Life Cycle

Immature Fasciola eggs are discharged in the biliary ducts and in the stool. Eggs become embryonated in water, eggs release miracidia, which invade a suitable snail intermediate host. In the snail the parasites undergo several developmental stages (sporocysts , rediae , and cercariae). The cercariae are released from the snail and encyst as metacercariae on aquatic vegetation or other surfaces. Mammals acquire the infection by eating vegetation containing metacercariae. Humans can become infected by ingesting metacercariae-containing freshwater plants, especially watercress . After ingestion, the metacercariae excyst in the duodenum and migrate through the intestinal wall, the peritoneal cavity, and the liver parenchyma into the biliary ducts, where they develop into adult flukes .

Peptidoglycan Cross-linking

In Gram negatives : cross linking between D-alanine and L-lysine is a direct covalent bond In Gram positives: 5 molecules of glycine make a bridge between D-alanine and L-lysine

Cytoadherence

In P. falciparum infections, membrane protuberances appear on the erythrocyte's surface 12-15 h after the cell's invasion. These "knobs" extrude a high-molecular-weight, antigenically variant, strain-specific erythrocyte membrane adhesive protein (PfEMP1) that mediates attachment to receptors on venular and capillary endothelium—an event termed cytoadherence.

Clay pipe stem fibrosis

In fatal schistosomiasis caused S. mansoni, fibrous tissue, reacting to the eggs in the liver, surrounds the portal vein in a thick, grossly visible layer

Categorization of Gram Positive Cocci

In general, the following characteristics Cytoplasmic lipid membrane Thick peptidoglycan layer Teichoic acids and lipoids are present, forming lipoteichoic acids, which serve as chelating agents, and also for certain types of adherence. Peptidoglycan chains are cross-linked to form rigid cell walls by a bacterial enzyme DD-transpeptidase. A much smaller volume of periplasm than that in gram-negative bacteria.

Trichomonas vaginalis life cycle

In the United States, an estimated 3.7 million people have the infection, but only about 30% develop any symptoms of trichomoniasis. Infection is more common in women than in men Female- found in urethra and vagina, male- in urethra and prostrate gland Sexual transmission is the primary mode of transmission.

Genotypic diagnosis

Includes the cause, and use of laboratory tests (endophenotypic). Based in genetic make up

Phenotypic Diagnosis

Includes the signs, symptoms, course, outcome, and response to treatment. Observable characteristics Isolation and characterization of pathogens Microscopic features - shape, size, staining reaction, cell structures Cultural Characteristics: Growth on artificial media; colony appearance; texture, size, shape, pigment, growth requirements Biochemical Characteristics - detection of presence or absence of particular enzymes or metabolic pathways Biotyping Serotyping: characterize based on antigen type Sensitivity to Antibiotics: for identification purpose

R group of penicillin

Increases resistance to stomach acids Increases absorption in the GI Resistance to penicillinases (beta lactamases) Increases spectrum of activity But no improvement in allergic reactions

Cleavage of rRNA

Inhibition of protein synthesis Removes adenine from specific sites on the 28s rRNA of the 60s ribosome Shiga/Vero toxin : Enterohemorrhagic E. coli and Shigella spp. In the intestine: Bloody diarrhea If it enters the blood: Hemolytic uremic syndrome (HUS) - death of RBC HUS, is a disease characterized by hemolytic anemia (anemia caused by destruction of red blood cells), acute kidney failure (uremia), and a low platelet count (thrombocytopenia).

Nucleic Acid antibiotics

Inhibit Nucleic Acid Synthesis and Function DNA Metronidazole Quinolones /Fluoroquinolones RNA Rifampin

Penicillins Mechanism of Action

Inhibit Peptidoglycan Synthesis-act on penicillin binding proteins (primarily transpeptidases) Transpeptidases Transglycosylase enzymes Carboxypeptidases Accumulation of peptidoglycan monomers (since they are unable to cross link in +nce of penicillin) leads to activation of autolytic Enzymes (Murine hydrolase): Lysis of cells Bactericidal in actively growing bacteria

Insects Vs. Arachnids

Insects Pediculus humanus (lice) Dermatobia hominis (flies/maggots) Cimex lectularius (bed bugs) Arachnids Sarcoptes scabiei (Itch mites) Eutrombicula spp. (Chigger mites) Dermacentor variabilis (Ticks) Dermacentor andersoni (Ticks) Ixodes dammini (Ticks) Ornithodorus spp (Ticks) Latrodectus mactans (Black widow spiders) Loxosceles spp. (Brown recluse spiders)

Recombination

Integration of donor DNA to the recipient chromosome/genome Stabilizing genetic information after gene transfer This results in new combinations of genes on the chromosomes involved Types A. Homologous DNA Recombination B. Site-Specific Recombination

Recombination

Interaction between two genetically different viruses Exchange of genetic material between different but related viral strains, occurring when infecting a cell simultaneously. By 2 mechanisms: Either by crossing over within the regions of significant base sequence homology (common with ds DNA viruses eg, Herpes 1 and 2) or, By exchange of segmented genome Reassortment-when two viruses with segmented genomes are simultaneously present and segments are mixed in progeny capsid Role in emergence of Epidemic Influenza strains

Reassortment of genes

Interaction between two genetically different viruses The mixing of the genetic material of a species into new combinations in different individuals. In particular, occurs among influenza viruses, whose genomes consist of eight distinct segments of RNA. (Genetic Shift) : Major changes

Major Protozoan Parasites

Intestinal -Entamoeba histolytica -Giardia lamblia -Cryptosporidium parvum -Cyclospora cayetanensis* -Cystoisospora belli * -Balantidium coli * mostly in immunocompromised host Urogenital -Trichomonas vaginalis Blood and tissue -Plasmodium spp. -Babesia spp. -Toxoplasma gondii -Leishmania spp. -Trypanosoma spp. -Naegleria fowleri -Acanthamoeba castellani

Negri Bodies

Intracytoplasmic inclusion body in rabies Is an accumulation of components of rabies virions in cytoplasm of neural cells.

Cowdry type A

Intranuclear inclusion body in Herpes infection

Pathogenesis of Chagas Disease

Invade and multiply inside: smooth muscle and ganglion cells in organs such as heart, walls of GIT; skeletal muscle cells or cells of RES Clinical symptoms: can be divided into: Acute phase: nodular lesion (chagoma) at the site of bite, Romana's sign, may include fever, lymphadenopathy Latent phase - asymptomatic, may last for many years Chronic phase - many years later; muscular degeneration and denervation of heart & GIT heart rhythm abnormalities that can cause sudden death; megaesophagus, megastomach, and megacolon

Inversion

Is a chromosome rearrangement in which a segment of a chromosome is reversed end to end Through the utilization of specific recombinases, a particular DNA sequence is inverted, resulting in an ON to OFF switch and vice versa of the gene located within or next to this switch. Many bacterial species can utilize inversion to change the expression of certain genes for the benefit of the bacterium during infection.

Transposons

Jumping Genes Mobile genetic elements The smallest transposon carries Insertion sequences -minimal genetic information required for transport and replication Transposases- transport; Resolvase or recombinase (Rec) is a nuclease which is involved in DNA recombination Can integrate and excise and take their gene to another place while leaving itself behind Can move to and from any DNA--phage, plasmid, bacterial genomes May carry additional genes such as genes coding antimicrobial resistance

Pathogenesis of Acanthamoeba castellani

Keratitis: associated with contact lens or eye trauma, Granulomatous amoebic encephalitis (GAE), plus Disseminated cutaneous and subcutaneous infections in HIV/immunocompromised patients

Cell Wall Less Forms

L forms Produced by the action of Lysozyme Antibiotics: cell wall synthesis inhibitors (beta-lactam (penicillin) Protoplast: from Gram positive (Stable L forms) Spheroplasts: from Gram negative (retain the outer membrane). Unstable L forms : they can divide and revert back to make peptidoglycan if moved to antibiotic free environment Formation of L forms may lead to infection after antibiotic treatment. Stable L-forms: L-forms that are unable to revert to the original bacteria.

Lab Diagnosis of Cryptosporidium parvum

Lab Diagnosis: Demonstration of oocyst in feces; unstained, acid fast or fluorescent staining

Strongloides stercoralis life cycle

Life cycle differs from Hookworm in 3 aspects: A. Eggs hatch into larvae in the intestine and before they are passed in feces (i.e we do not see eggs of the parasite in stool examination) B. Larvae can mature into filariforms in the intestine and cause autoinfection C. Free living, non parasitic cycle can occur outside the human host Once Strongyloides enters the skin it follows the path similar to hook worms.

Plasmodium: Life Cycle

Life cycle involves two hosts. During a blood meal, a malaria-infected female Anopheles mosquito inoculates sporozoites into the human host . Sporozoites infect liver cells and mature into schizonts , which rupture and release merozoites . (Of note, in P. vivax and P. ovale a dormant stage [hypnozoites] can persist in the liver and cause relapses by invading the bloodstream weeks, or even years later). After this initial replication in the liver (exo-erythrocytic schizogony ), the parasites undergo asexual multiplication in the erythrocytes (erythrocytic schizogony) . Merozoites infect red blood cells . The ring stage trophozoites mature into schizonts, which rupture releasing merozoites . Some parasites differentiate into sexual erythrocytic stages (gametocytes) . Blood stage parasites are responsible for the clinical manifestations of the disease. The gametocytes, male (microgametocytes) and female (macrogametocytes), are ingested by an Anopheles mosquito during a blood meal . The parasites' multiplication in the mosquito is known as the sporogonic cycle . While in the mosquito's stomach, the microgametes penetrate the macrogametes generating zygotes . The zygotes in turn become motile and elongated (ookinetes) which invade the midgut wall of the mosquito where they develop into oocysts . The oocysts grow, rupture, and release sporozoites , which make their way to the mosquito's salivary glands. Inoculation of the sporozoites into a new human host perpetuates the malaria life cycle.

Bactoprenol

Lipid carrier molecule that transports peptidoglycan precursors across the cytoplasmic membrane

Stool/urine sample

Macroscopic examination Microscopic examination Wet mount Permanent stains Stool concentrates Demonstrate: Cyst, trophozoite, egg, larvae, adult Culture

Biofilms (Glycocalyx)

Made of mucopolysaccharide surround populations of cells to provide: Adhesion (devices & even in tissue) Protection against: Phagocytosis Dehydration Antibiotic/antibodies penetration

Pathogenesis of Diphyllobothrium latum

Mechanical presence causes most symptoms; and malnutrition Clinical Disease: mostly asymptomatic. Since they can live for upto 25 years, symptoms vary: Intestinal : usually mild abdominal discomfort, bloating, diarrhea. Migrating proglottids: acute abdominal pain and intestinal obstruction, cholangitis (inflammation and obstruction of the bile ducts) and cholecystitis (inflammation of gallbladder) Megaloblastic anemia: With heavy load, B12 deficiency (the parasite absorbs lots of vitamin B12) Neurological sequelae of vitamin B deficiency

Filtration

Mechanical removal using filters Any particle bigger than the diameter of the filter pores gets trapped. The most common bacterial filters are nitrocellulose membranes with pore size of 0.22 micrometers Used for heat sensitive liquids, such as enzymes and solutions for intravenous administration Also used to sterilize air in safety cabinet

Adsorption/ Attachment to Target Cell

Mediated by molecular interaction between virus and target cell Viral attachment structures: Surface structures on the capsid or envelope -Viral attachment proteins (VAP)/peplomers/spikes -Determine host/tissue specificity -High mutation rate in VAP can result in change in host specificity or avoid immune response eg. Influenza virus - hemagglutinin (HA) HIV - glycoprotein (gp)120 Receptors on target cell: are proteins or carbohydrates on glycoproteins and glycolipids Examples -CD4 and CxCR4/CCR5 (a chemokine receptors) on T helper cells, and Macrophages - for HIV -ICAM-1 on epithelial cells for rhinovirus -Sialic acid on epithelial cells for influenza virus Permissiveness = allowing Entry + Replication

Blood &Tissue Protozoa

Medically Important: Plasmodium spp. Babesia microti Toxoplasma gondii Leishmania spp. Trypanosoma spp. Naegleria fowleri Acanthamoeba castellani

Semisynthetic Penicillins

Methicillin, nafcillin, oxacillin, ampicillin, amoxycillin Resistant to beta-lactamase Increased stability to stomach acid Increased spectrum of activity Activity - similar to natural penicillins with increased activity against Gram negative rods and beta-lactamase producing organism

Culture

Method of multiplying microbial organisms by letting them reproduce in predetermined culture media Pure culture: culture with one type of bacteria, theoretically derived from a single cell

Treatment and prevention of Giardia lamblia

Metronidazole or nitazoxanide with furazolidone (Nitrofuran antimicrobial, works by crosslinking of DNA) Prevention and control: Personal and public hygiene Avoidance of contaminated water and food Boiling or filtration (water from streams/lakes) Proper filtration system in municipal water supplies (since cysts are resistant to standard chlorination) Avoidance of high-risk sexual behaviour

Diagnosis of Leishmaniasis

Microscopic examination Of bone marrow, spleen, liver or lymph node biopsy, Of scrapings from margin of lesions demonstrate parasites inside macrophages Serology: Direct Agglutination Test (DAT) rK39 test: Serologic test using the cloned antigen rK39 instead of whole Leishmania parasites. The rK39 antigen, which consists of 39 amino acid repeats of a kinesin-like gene found in L. chagasi, is used in an enzyme-linked immunosorbent assay (ELISA) format and rapid diagnostics Novy-MacNeal-Nicolle (NNN) medium is used to grow Leishmania. It consists of 0.6% sodium chloride (NaCl) added to a simple blood agar slope. NNN can also be used to grow Trypanosoma cruzi. leishmanin test (Also called as Montenegro test) is a delayed hypersensitivity test for cutaneous leishmaniasis, In this test, killed Leishmania antigens are injected intradermally. A positive reaction is indicated by the appearance of a palpable nodule in 48 to 72 hours

Diagnosis of Chagas Disease

Microscopy Blood - flagellate form only during acute form, Tissue biopsy: amastigote form Culture: Cell culture/culture in NNN medium Animal inoculation -intra-peritoneal inoculation, mice Serology Xenodiagnosis: Reduviid bug is allowed to feed on a patient, then parasites are detected in the bugs

Syncytia Formation

Multi-nucleated syncytial cells are often the result of infections by enveloped viruses that induce cell fusion.

Pathogenesis of Leishmaniasis

Multiply inside macrophages and other cells. Kala-azar (Visceral form)/Black fever/Dumdum fever: asymptomatic to rapidly fatal disease affects organs of the reticuloendothelial system (RES) Liver, spleen and bone marrow IP: several wks to a year Gradual onset of fever, chills, sweating, diarrhea, anemia Hyperpigmentation of skin Persistence results in Post-Kala-azar dermal leishmaniasis: hypopigmented/nodular lesions Cutaneous and muco-cutaneous forms: pruritic lesions enlarge and ulcerate

Treatment of trichinosis

NO effective treatment, anthelmintic drugs cannot reach the larvae in tissue: Mebendazole halt new larvae production in intestine Steroids for treatment of inflammatory symptoms Prevention: Education regarding transmission Proper cooking of meat (pork/bear meat); Strict regulation regarding pigs feed- avoid feeding pigs with uncooked garbage.

Antibiotic terminology

Narrow spectrum: active against one or few types of pathogens Broad spectrum: active against a wide variety of pathogens Bactericidal: Kills the pathogen, irreversible Bacteriostatic: Inhibit the growth of the pathogen, reversible Empirical therapy: initial selection of antibiotics based on clinical findings Bacteriostatic drug: on withdrawal of drug - growth of agent. Assists the host defense by limiting the populations size

Pathogenesis of Brown Recluse bite

Necrotic arachnidism (Dermonecrotic disease) Bite painless initially Several hours later-itching, swelling and soreness in area of bite Vesicle or bleb formation General symptoms (chills, headache, nausea) Within 3-4 days: ulceration of the bleb and radiating necrosis Diagnosis: Clinical as well as identification of typical spiders

Molecular Methods

Nucleic acid based tests Highly specific, quite sensitive, safe, and fast Historically used for pathogens difficult to culture, highly contagious, nowadays for rapid diagnosis Most commonly used are Amplification: Polymerase chain reaction (PCR) - require primers Hybridization; Detection and localization in biopsy:- requires labelled probes DNA Probes labelled with enzymes or fluorescent compounds Sequence analysis: 16s RNA subunit used to identify bacteria

Diagnosis of Dracunculiasis

Observation of the lesions and recovery of the adult/larval worms while flooding the ulcer with water Radiological examination

Hydrogen peroxide

Oxidizing agent Attacks sulfydryl groups in proteins and modifies them kills most bacteria, kills spores Antiseptic - to clean wounds and contact lenses

Halogens

Oxidizing agents, Denature proteins kill the micro-organism by cross-linking essential sulfydryl groups in enzymes to form the inactive disulfide Chlorine: used in purification of water and as disinfectants on inanimate objects (Sod. hypochlorite) Iodine: Two forms, Tincture of iodine (2% solution of iodine and potassium iodide in ethanol) is used to prepare the skin prior to blood culture. Iodophores are complexes of iodine with detergents that are frequently used to prepare the skin prior to surgery because they are less irritating than tincture of iodine As antiseptics - to clean skin or disinfect wounds

Filarial Elephantiasis

Pathogenicity: chronic and debilitating Acute phase: recurrent fever, inflammation of lymphatic channels (lymphangitis) and lymph nodes (lymphadenitis); Due to release of endotoxin like molecule by Wolbachia (rickettsia like bacteria as endosymbiont in Wuchereria) Chronic: presence of adult worms and host reactivity eventually obstructs the lymphatic vessels, causing edema in the extremities-arms and legs; lymph nodes enlarge Thickening & hypertrophy of the tissues- Affected part enormously enlarged: Filarial elephantiasis Males-hydrocele or swelling of the scrotum The stretched skin is susceptible to traumatic injury and bacterial infections may complicate Chyluria: escape of chyle through urine

Naturally occurring Penicillins

Penicillin G Acid labile, Narrow spec Penicillin V Acid Stable, Narrow spec Active against Gram positive bacilli and cocci, Gram negative cocci, and spirochetes Poor activity against G -ve rods Side effects: allergic reaction Most clinical isolates have developed resistance to these drugs.

Enterobius vermicularis

Pinworm Epidemiology: Worldwide - 500 million infections (estimated) Most common helminth infection in US; small children, crowding- day care centers, schools and mental institution; Most common in temperate region (cold weather); poor hygiene; No animal reservoir Transmission: fecal-oral, ingesting pinworm eggs either directly or indirectly. Autoinfection (Retrofection) Retrofection: infection with pinworms in which the eggs hatch on the anal skin and mucosa and the larvae migrate up the bowel to the cecum where they mature

Pathogenesis of Enterobiasis

Pinworm infection Mild to severe disease depending on worm burden; Severe type IV immune response to secretion of the female, itching/pruritus in skin around the anal area. Clinical Disease: IP: 1 to 2 months or longer Severe itching : perianal and vaginal irritation caused by the female migration or presence of egg and larvae. The itching results in insomnia and restlessness Secondary bacterial infection: due to scratching Gastrointestinal symptoms: pain, nausea, vomiting, etc. may develop. Adult worm enters appendix or genital tract in females leading to inflammation and granuloma. Eosinophilia and elevated IgE Type IV reaction to female laying eggs, just like it is poison oak

Phenotypic mixing

Progeny virus acquiring coat components of both the viruses; or genome of one virus surrounded by capsids or both capsids and envelope of other virus May occur between related viruses, e.g. different members of the Picornavirus family, or between genetically unrelated viruses, e.g. Rhabdo- and Paramyxo- viruses. In the latter case the two viruses involved are usually enveloped since it seems there are fewer restraints on packaging nucleocapsids in other viruses' envelopes than on packaging nucleic acids in other viruses' icosahedral capsids.

Virulence factor

Properties of a pathogen that help it cause disease

Prokaryotes vs Eukaryotes

Protein synthesis in bacteria =n-formyl methionine as the first amino acid; in eukaryotes it is methionine

Exotoxins

Proteins secreted by many bacteria Three types: A-B Toxin Membrane damaging Toxins Superantigens

Antihelminthic Inhibition of Neuromuscular Action

Pyrazinoisoquinoline: Praziquantel Calcium agonist, tetanic muscular contraction as well as destruction of the tegument Tetrahydropyrimidine: Pyrentel pamoate- cholinergic agonist Piperazines - Diethylcarbamazine (DEC): stimulate cholinergic recep. Muscular paralysis, enhances adherence of leucocyte on parasite Avermectins - Ivermectin Interacts with chloride channel, blocks neuromuscular action Phenols-Niclosamide Acts by uncoupling of oxidative phosphorylation in mitochondria-loss of helminth ATP-Immobilization

Detergents

Quaternary ammonium salts "Surfactants" disrupt cell membrane Composed of a long-chain lipid soluble- hydrophobic end and polar hydrophilic end. Effective against Gram negative cell and enveloped viruses Used as skin antiseptics

Replication Sites

RNA viruses replicate in the cytoplasm DNA viruses replicate in the Nucleus With a few exceptions Orthomyxo in the Nucleus and Poxviruses in the Cytoplasm In both compartments: Retroviruses and Hepadnaviruses

Pathogenesis of Balantidium coli

Release of proteolytic and cytotoxic sustances Causes invasion and ulceration Extraintestinal-rare Clinical disease: Abdominal pain and tenderness, tenesmus, Bloody diarrhea/dysentery similar to that of Entamoeba histolytica

Treatment of Dracunculiasis

Removing the whole worm and caring for the wound in general. No specific drug to treat or prevent GWD. Prevention and control: no vaccine to prevent GWD Global eradication program-safe drinking water and education, Expected to be eradicated in the near future Filtering drinking water, using a fine-mesh cloth filter like nylon

Griffith's experiment

Reported in 1928 by Fredrick Griffith, was the first experiment suggesting that bacteria are capable of transferring genetic information through a process known as transformation Rough strain: Non capsulated (Non virulent) Smooth Strain: Capsulated (Virulent)

Culture Characteristics

Requirements: oxygen, Temp, pH, osmotic pressure, growth factors, etc Colony morphology: Appearance on culture media - Selective, differential, enriched Size, Texture (rough, smooth) hemolysis, pigment etc...

Site-Specific Recombination

Requires no homology It is an integration not exchange Requires restriction endonucleases and sites for the endonucleases on both DNA Foreign DNA may be circular or linear End result is the sum of the existing genome plus the integrated DNA Three major roles: Conjugation: Integration of a fertility factor to make an Hfr cell Transduction: Integration of temperate phage DNA into bacterial chromosome to create a prophage Transposition: Movement and insertion of transposons

Carboxypeptidase

Restriction enzyme that cuts to the left of carboxy terminal Remove terminal D alanine from the pentapeptides in peptidoglycan Inhibited by penicillins

Different types of mutations

Result in variety of mutants: Lethal mutant - due to inactivation of essential genes, can't replicate Defective mutant- deletion/mutation of gene/s: able to replicate with the help of other viruses Host range mutant - change of host/tissue specificity Attenuated mutant - causes less serious/no disease (vaccines) Conditional mutant: (eg temperature sensitivity of influenza live vaccine - can multiply at lower temp of URT but not LRT

Pathogenesis of Cyclospora cayetanensis

Rupture of epithelial cells during release of oocyst Incubation Period: an average of 7 days Watery diarrhea (most common), loss of appetite, weight loss, cramping, bloating, increased gas, nausea, fatigue If not treated, persistent watery diarrhea lasting over several days Typically, patients who come in with a persistent watery diarrhea lasting over several days may be suspected of harboring the disease, especially if they have traveled to a region where the protozoan is endemic.

General Pathogenesis of Cestodes

Sequestering host's nutrients (due to adults residing in intestines) = malnourishment/developmental and/or physical retardation in young people Massive infections - blockage of the intestine Excreting toxic waste - immune response Space occupying lesions - larvae in tissue Some live for many years - tissue damage increases with time

Fungal Culture

Sabouraud dextrose agar (SDA): a common culture media Slightly acidic, may contain antibacterial drugs to suppress bacterial growth Two cultures - at 25 oC and 37 oC - detect thermal dimorphism Not reported negative until 4 weeks Gross colony appearance such as color, texture etc.; and Pigmentation Microscopic examination: examine hyphal and spore structures Lactophenol Cotton Blue (LPCB) mount-commonly used Components of LPCB stain: Lactic acid: preservative Phenol: disinfectant Cotton blue: stain Glycerine: hygroscopic agent

Chlorhexidine

Salts dissociate and release the positively charged chlorhexidine cation. The bactericidal effect is a result of the binding of this cationic molecule to negatively charged bacterial cell walls. At low concentrations of chlorhexidine, this results in a bacteriostatic effect; at high concentrations, membrane disruption results in cell death.

Laboratory Diagnosis of parasites

Samples: based on suspicion of organ invasion Stool samples: a series of 3 specimens on alternate days (within 10 days) Urine sample Blood and tissue etc.

Limitations of Koch's postulates

Some pathogens are found as normal flora in certain % of the population Not all microorganisms are cultivable, eg, Treponema pallidum, Mycobacterium leprae Finding an experimental animal model for all microorganism is difficult Some diseases have a synergistic etiology of two or more agents.

Eosin Methylene blue (EMB) agar and MacConkey agar

Selective and differential media Only Gram negative bacteria grow (Coliforms) Differentiate between lactose fermenter and non fermenter LF: Lactose fermenting colonies NLF: Non lactose fermenting colonies EMB agar: contains dyes that are toxic for Gram positive bacteria and bile salt which is toxic for Gram negative bacteria other than coliforms. EMB is the selective and differential medium for coliforms Lactose fermenters in EMB agar give a distinctive metallic green sheen (due to the metachromatic properties of the dyes) MacConkey agar: LF colonies: pink, NLF: gray/colourless

Treatment of Cryptosporidium parvum

Self limiting in healthy. No effective treatment, Immunocompromised may use paromomycin, nitazoxanide Prevention and control: Improved personal hygiene and sanitation, purification of water supply including filtration (since cysts are resistant to standard chlorination)

Penetration and Uncoating

Several mechanisms Enveloped viruses Fusion: Enveloped virus fuses with host cell membranes, pH dependent; At neutral pH- fusion on the surface and release of the genome takes place. Endocytosis: At acidic pH the whole viral particle is engulfed (Endocytosis) and release takes place in the cytoplasm Naked viruses Endocytosis : Naked viruses are taken up by receptor mediated phagocytosis or, Viropexis: direct penetration of the genome Naked virus binds to receptor sites on cellular membrane and inject the nucleic acid. Uncoating Capsid digested or opened up AND nucleic acid released

Blood agar

Sheep Blood agar- enriched and differential media Enriched: with blood Differential: hemolytic character (alpha, beta and gamma/non)

Protozoa

Single cells; eukaryotic cell structure Surrounded by either a plasma membrane alone or with an exterior flexible pellicle Extracellular and intracellular infections May have two or more forms/stages Trophozoite is the motile, metabolically active, replicating form Cyst is the dormant, non-replicating form that is adapted for survival in the environment. If it does not have a cyst form, it must be transmitted via a vector or direct contact

Viroids

Single circular RNA, no protein coat; identified only in plants

Major differences between C. cayetanensis and C. parvum

Size difference — C. parvum is smaller; Differing results from modified acid-fast staining -C. parvum has consistent red staining; and Autofluorescence under UV light — C. cayetanensis does, C. parvum does not.

Bacterial cell size

Size ranges between 0.2-5 µm The smallest bacteria, Mycoplasma = largest virus (Pox virus), measures about 0.1µ to 0.2µ m in diameter

Pathogenesis of Hookworm infection

Skin manifestation: ground itch - at site of penetration Pulmonary manifestation: migrating larvae (Loeffler's syndrome) Intestinal: Attaches to the intestinal mucosa, bleeding, anorexia Ulcer-like symptoms, and chronic intestinal BLOOD LOSS leading to anemia, diarrhea and abdominal discomfort. Huge appetite with PICA (desire to eat unusual substances, such as dirt, clay, paint)

Ascaris lumbricoides

Soil-transmitted helminths Giant nematode (roundworm) Epidemiology: Worldwide -prevalent with poor sanitation; eggs survive in nature; persist in feces and sewage; No animal reservoir known (however, a swine species can infect swine farmers) The most common helminthic infection in the world - about ¼ of world population infected. More common in tropical and subtropical climate. Occurs in Southern USA Is regarded as the largest intestinal nematodes parasitizing man. Male: 15-25 cm, Female: 25-40 cm Male has curved posterior end with two copulatory spicules Transmission: fecal-oral; ingestion of eggs Soil transmitted helminth

Hookworm

Soil-transmitted helminths (parasitic worms) Ancylostoma duodenale - old world hook worm Necator americanus - new world hook worm Epidemiology: world wide; second most common roundworm of humans; infect nearly 1/5 of world's population, warm, shady, sandy soil; common in area where human feces are used as fertilizer Transmitted through direct skin penetration of skin by larvae in soil Risk factor: walking bare foot

High Frequency Plasmids

Some F plasmids can be integrated into the host chromosome because they contain insertion sequences. These are called Hfr plasmids Can transfer chromosomal genes from the donor to the recipient

Competence

Some bacteria are able to take up DNA naturally. However, these bacteria only take up DNA in a particular time during their growth cycle when they produce a specific protein called a competence factor. At this stage the bacteria are said to be competent. Other bacteria are not able to take up DNA naturally. However, in these bacteria competence can be induced in vitro by treatment with chemicals (e.g. CaCl2). The DNA first binds to the surface of the competent cells on a DNA receptor, and passes through the cytoplasmic membrane

Frame shift mutation

Sometimes, during replication, one or a few adjacent base pairs (nucleotides) have been inserted to or deleted from the DNA. Shifts reading frame. Missense mutation: base changes result in production of different amino acids but the resulting protein may be functional or non functional (which depends on the importance of area affected by the mutation) Non sense mutation: One or more of 3 non sense codons (UAG, UAA, UGA), normally cause termination of the polypeptide chain elongation. If a nonsense codon is formed within a gene by mutation of a sense codon, the protein synthesis is terminated prematurely and only partial polypeptide is produced

Pathogenesis of Fungi

Source Exogenous: Environmental exposure, spore or hyphal form can be infectious Some are geographically restricted Endogenous: Overgrowth of normal flora Route of Entry: respiratory, cutaneous, or through mucus membranes Virulence factors: Include -Cell wall components are inflammatory stimulants -Adhesion factors -Capsules -Survival inside macrophages -Hydrolytic enzymes (proteases, phospholipases) -Thermal dimorphism: ability to grow at 37oC -Mycotoxins: toxic metabolites produced in the environment; associated with mycotoxicosis Some fungi produce melanin which interfere with the oxidative killing inside macrophages.

Transmission of Parasitic Disease

Source: Exogenous (from out side) Mode of transmission Ingestion: Contaminated water or food with human/animal waste Raw or undercooked beef/pork/fish Direct penetration: Arthropod borne, larval-directed skin penetration Transplacental Sexual contact

Categorization of Gram Positive Rods

Special techniques for endospore staining include the Schaeffer-Fulton stain (uses malachite green and safranin; spores appear green) and the Moeller stain (uses carbol fuchsin and methylene blue, spores appear red)

Treatment of Black Widow bite

Specific antivenom- treatment of choice Muscle spasm: administration of calcium gluconate or muscle relaxants Prevention and Control Good housekeeping-dusting webs and removing debris from around homes and adjacent sheds Discouraging children from playing on woodpiles and in woodsheds

Morphology of Plasmodium spp.

Sporozoan, exists in different forms (sexual and asexual reproduction). Sporozoites : infective to liver cells Trophozoites: early stages in liver/RBC Schizont - mature malarial parasite, contains many merozoites. Merozoites: infective to RBC Gametocyte: inside RBC

Enzyme test

Spot test: rapid colorimetric assays Detect Beta lactamases; eg. ESBL (Nitrocef test) Chloramphenicol modifying enzyme-Chloramphenicol acetyltransferase Faster

Homologous DNA Recombination

Stabilizes linear genes after genetic transfer It is an exchange of piece of DNA: loss of old information, replaced by new Requires long region of homology and a series of recombination enzymes (recA, recB, etc)

Stages of Viral Replication

Stages: Adsorption/Attachment - Adsorption: binding of virus to specific molecule on host cell Entry/penetration - the virus enters host cell Uncoating- the viral nucleic acid is released from the capsid Macromolecular Synthesis- viral components are produced Assembly- new viral particles are constructed Release - assembled viruses are released by budding (exocytosis) or cell lysis

Cryptosporidium parvum Life cycle

Stages: several forms Oocyst (with sporozoites inside): inactive: Infective and diagnostic stage: Trophozoite; actively dividing Merozoite Gametes: micro and macro gamonts Gamete fusion - zygote Oocyst

Diagnosis of Trichuriasis

Stool examination- bile stained, barrel shaped egg with polar (mucous) plugs The eggs in the stool contain unsegmented ovum

Diagnosis of Fasciola hepatica

Stool examination-operculated eggs To differentiate from F. buski: bile examination Eggs: broadly ellipsoidal, operculated, bile stained, and measure 130-150 μm by 60-90 μm.

Diagnosis of Ascariasis

Stool for eggs and parasite (occasional adult worms, usually eggs) Sputum, bronchoscopically obtained washing, and gastric lavage may reveal larvae of the Ascaris Imaging Studies: Patchy infiltrate on chest radiograph or worms seen in abdominal radiograph Infusion of the contrast medium barium sulfate, a radioopaque salt, coats the lining of the digestive tract, allowing accurate X-ray imaging of this part of the abdomen. Adult Ascaris may be seen as filling defects.

Beta Lactamase Inhibitors

Structural analogues of beta-lactams: have little antibacterial activity but bind strongly to beta lactamase thus protect penicillins/cephalosporins. Given together with beta lactams Clavulanic Acid Augmentin=Clavulanic Acid+ Amoxycillin Sulbactam Unasyn=Sulbactam + Ampicillin Tazobactam Zosyn=Tazobactam + Piperacillin Avibactam Avycaz=Avibactam +Ceftazidime (Cephalosporin) Activity: improved against beta-lactamase producing bacteria

Dapsone and Para-Aminosalicylic Acid

Structure Similar to sulfonamides Mechanism of action Similar to sulfonamides Pharmacology Narrow Spectrum: Mycobacterium Mechanisms of Resistance Same as sulfonamides

Spheroplast

The complexity of the Gram negative cell wall results in innate resistance to enzymatic destruction of cell wall. Thus, Gm -ve bacteria with damaged cell walls become Spheroplasts i.e, they assume spherical shape even in a non-isotonic medium because of their resistance to differences in osmotic pressure between the extracellular and intracellular compartments.

Chloramphenicol

Structure: Nitrobenzene structure, no derivatives Mode of action: Binds to 50S: Inhibits protein synthesis by inhibiting peptidyl transferase or elongation stage Pharmacology: bacteriostatic Broad spectrum: including anaerobes Side effects: bone marrow toxicity- aplastic anemia; Gray-Baby syndrome Resistance: enzymatic modification and decreased permeability. Inhibits mitochondrial protein synthesis (mitochondria have 50s ribosome) in host cell - a reason for its toxicity in the bone marrow. Another explanation for toxicity is the drug acting as hapten.

Cestodes

Structure: Tape worms Ribbon like, segmented worms (size varies - some reach 25 meters) Do not have GIT - food absorbed from host GIT Anterior end: scolex- suckers with/out hooks for attachment Body: Strobilla Composed of proglottids (segments) Reproductive structures filled with eggs, are hermaphrodite Break off and pass out of body in stool use flame cells for excretion

Bacitracin

Structure: a large, complex cyclic peptide Mechanism of Action Binds to Bactoprenol and inhibits transportation of peptidoglycan precursors Bactericidal Pharmacology: narrow spectrum, Gram positive, nephrotoxic, Topical application Resistance: decreased penetration

Tetracyclines and derivatives

Structure: consists of four joined cyclic rings. Mechanism: binds to 30s - prevents binding of tRNA to mRNA Pharmacology: Bacteriostatic, broad spectrum- Many G+ve, G-ve bacteria; Mycoplasma, Rickettsia, Chlamydia -transported actively into prokaryotes but not into eukaryotes because of energy-dependent transport system present in prokaryotes, but not in eukaryotic cells. Side effects: Discoloration of teeth Calcium and Iron chelator - not for children under 8 and pregnant women Suppress Normal flora: Gastrointestinal, Vaginal tract Photosensitivity Mechanisms of Resistance Active efflux: most common Decrease permeability Alteration of ribosomal binding site Enzymatic modification (acetylation)

Treatment and Prevention of Onchocerciasis

Surgical removal of nodules (adults) Ivermectin (only kills the larvae; not the adult) Doxycycline (promising result, kills wolbachia-leads to death of adult) Use of insect repellant such as DEET WHO is close to eradicating it Suramin kills adult worms, but is quite toxic - given only for those with eye disease There is a promising new treatment using doxycycline that kills the adult worms by killing the Wolbachia bacteria on which the adult worms depend in order to survive (CDC).

Capsules (Slime layer)

Surround single cells Composition: Mucopolysaccharides Multivalent - poor immunogen in children <2 Polypeptides Multivalent - still a poor immunogen Function Adhesion Protection against: Phagocytosis Dehydration Antibiotic penetration Gycocalyx = capsule (means sugar coat) Multivalent antigens: having multiple binding sites for antibodies Glycosaminoglycans or mucopolysaccharides are long unbranched polysaccharides consisting of a repeating disaccharide unit. The repeating unit consists of a hexose (six-carbon sugar) or a hexuronic acid, linked to a hexosamine (six-carbon sugar containing nitrogen)

Babesia: Life cycle

The Babesia microti life cycle involves two hosts, which include a rodent, primarily the white-footed mouse and a tick in the genus Ixodes. During a blood meal, a Babesia-infected tick introduces sporozoites into the mouse host . Sporozoites (pyriform bodies) enter erythrocytes and undergo asexual reproduction (budding) . In the blood, some parasites differentiate into male and female gametes, although these cannot be distinguished by light microscopy . The definitive host is the tick. Once ingested by an appropriate tick , gametes unite and undergo a sporogonic (sexual) cycle resulting in sporozoites . Transovarial transmission (also known as vertical, or hereditary, transmission) has been documented for "large" Babesia species but not for the "small" Babesia, such as B. microti . Humans enter the cycle when bitten by infected ticks. During a blood meal, a Babesia-infected tick introduces sporozoites into the human host . Sporozoites enter erythrocytes and undergo asexual replication (budding) . Multiplication of the blood-stage parasites is responsible for the clinical manifestations of the disease. Humans usually are dead-end hosts. However, human-to-human transmission is well recognized to occur via contaminated blood transfusions

Inclusion Bodies

The Negri body is an accumulation of rabies virions (belongs to Rhabdoviridae) in cytoplasm of neural cells Intranuclear inclusion body: From lesion of CMV (belongs to herpesviridae) infection-Cowdry type A (Owl' s eye)

HBsAg Rapid Test Principle

The Rapid Test is based on the principle of chromatographic immunoassay for qualitative detection of the surface antigen of hepatitis B virus (HBsAg) in human whole blood, serum, and plasma samples. Monoclonal and polyclonal antibodies are employed to identify HBsAg specifically. This HBsAg Rapid Test employs chromatographic lateral flow device. Colloidal gold conjugated monoclonal antibodies reactive to HBsAg are dryimmobilized onto a nitrocellulose membrane strip. When the sample is added, it migrates by capillary diffusion trough the strip rehydrating the gold conjugate. If present, HBsAg will bind with the gold conjugated antibodies forming particles. These particles will continue to migrate along the strip until the Test Zone (T) where they are captured by anti-HBs antibodies immobilized there and a visible red line appears.

Quorum sensing

The ability of bacteria to sense the presence of other bacteria via secreted chemical signals. Regulation of gene expression in response to fluctuations in cell-population density. Some genes are only turned on when bacteria are present in high concentrations. Many bacteria can use "quorum sensing" to detect presence of specific autoinducer chemicals used for measuring cell density. These autoinducers are specific peptides (Gram positive bacteria) or homoserine lactones (Gram-negative bacteria). Autoinducer is produced in low amounts by all cells, diffuses freely across membrane, so concentration inside and outside cell is same. As cell number increases, autoinducer conc. increases until it is sufficient to bind to activator, turn on transcription of specific genes. Example: some virulence genes of pathogens are controlled by quorum sensing. Until a sufficient density of cells is present, cells don't turn on these factors. Signal molecules produced by individual cells do not have an effect until the bacterial population density is sufficient to provide a concentration of molecules, which then cross cell membranes and activate the manufacture of such cellular products as toxins, enzymes or surfactants

Hydatid cyst

The cyst vary considerably in size depending on where in the body they are formed, which may be almost any organ of the body. In the liver (the most common organ affected) it may be approximately 20cm in diameter and those found in the peritoneal cavity may sometimes be very much larger, containing several litres of fluid. For example one case has been reported of a cyst 50cm in diameter, containing 16 liters of fluid. We have to remove the intact cyst to prevent type I hypersensitivity Hydatid (Echinococcus): Larval stage, i.e, a bladder which multiplies by budding and forms many daughter and grand-daughter bladders. On the wall of these cysts, brood capsules are produced, inside which lie scolices.

Pathogenesis of Toxocariasis and Baylisarcaris

The larvae from the intestine wanders in different organs and disintegrate causing inflammatory response, granuloma, and tissue damage. Larval form migrate to lungs, liver, heart, kidneys, CNS, eyes Toxocara species are the most common causes of VLM and OLM whereas Baylisarcaris procyonis is the most common cause of NLM Disease expression : depends on the organs affected Intestinal: initial manifestation fever, anorexia and abdominal discomfort (During larval penetration of GIT) Pulmonary: cough, wheezing Ocular: Blindness Death can occur due to respiratory failure, cardiac arrhythmias or brain damage

Nutritional factors

The most important elements necessary for synthesis of bacterial structural components (Carbohydrate, lipid, protein, nucleic acid) are hydrogen, oxygen, carbon, nitrogen, phosphorus and Sulphur. Hydrogen and Oxygen are made available from water added to the culture medium. Carbon and Nitrogen: Carbohydrate (sugars) is the principal source of carbon which is degraded by the bacteria either by oxidation or by fermentation. The oxidation or fermentation process provides energy in the form of ATP. Nitrogen is a major component of protein and nucleic acids and its main source is ammonia, usually in the form of an ammonium salt Sulphur and Phosphorus: Sulphur forms part of the structure of several co-enzymes and cysteinyl and methionyl side chains of proteins. Most bacteria use sulphate as a sulphur source and reduce it to hydrogen sulphide. Phosphorus is required as a component of nucleic acids, ATP, co-enzymes NAD and flavins. Mineral sources: required in trace amounts. Can be provided in tap water or as contaminants of other medium ingredients.

Hemagglutination

The red blood cells that are attached to virus particles form a lattice that coats the well

Human T-cell lymphotropic virus 1

The only human oncogenic retrovirus identified, uses more subtle mechanisms of leukemogenesis. It encodes a protein (TAX) that transactivates gene expression, including genes for growth-stimulating cytokines (e.g., interleukin-2 [IL-2]).

Intestinal Amoeba differential diagnosis

The presence of commensals amoebas in the intestine may make microscopic diagnosis difficult. E. histolytica can be distinguished from the other amoebas by trophozoite and cyst morphology. Number of nuclei in the cyst - maximum 4. Shape of the nuclei - central karyosome. Presence of ingested RBC in trophozoite are characteristic of E. histolytica

Septic

The presence of microorganisms in tissue.

Toxoplasma gondii life cycle

The oocyst/cyst is rapidly digested by the acidic-pH gastric secretions. Bradyzoites or sporozoites are released, enter the small-intestinal epithelium, and transform into rapidly dividing tachyzoites. The tachyzoites can infect and replicate in all mammalian cells except red blood cells. Once attached to the host cell, the parasite penetrates the cell and forms a parasitophorous vacuole within which it divides. Parasite replication continues until the number of parasites within the cell approaches a critical mass and the cell ruptures, releasing parasites that infect adjoining cells. Most tachyzoites are eliminated by the host's humoral and cell-mediated immune responses. Tissue cysts containing many bradyzoites develop 7-10 days after systemic tachyzoite infection. These tissue cysts occur in various host organs but persist principally within the central nervous system (CNS) and muscle. The development of this chronic stage completes the nonfeline portion of the life cycle. Active infection in the immunocompromised host is most likely to be due to the spontaneous release of encysted parasites that undergo rapid transformation into tachyzoites within the CNS. The principal (feline) stage in the life cycle takes place in the cat (the definitive host) and its prey. The parasite's sexual phase is defined by the formation of oocysts within the feline host. This enteroepithelial cycle begins with the ingestion of the bradyzoite tissue cysts and culminates (after several intermediate stages) in the production of gametes. Gamete fusion produces a zygote, which envelops itself in a rigid wall and is secreted in the feces as an unsporulated oocyst. After 2-3 days of exposure to air at ambient temperature, the noninfectious oocyst sporulates to produce eight (from 2 sporocysts, each with 4 sporozoites) sporozoite progeny. The sporulated oocyst can be ingested by an intermediate host, such as a person emptying a cat's litter box or a pig rummaging in a barnyard. It is in the intermediate host that T. gondii completes its life cycle.

Quorum sensing

The regulation of gene expression in response to fluctuations in cell-population density. Quorum sensing bacteria produce and release chemical signal molecules called autoinducers that increase in concentration as a function of cell density. The detection of a minimal threshold stimulatory concentration of an autoinducer leads to an alteration in gene expression. Gram-positive and Gram-negative bacteria use quorum sensing communication circuits to regulate a diverse array of physiological activities

Loa Loa: life cycle

The vector for Loa loa filariasis are flies of the genus Chrysops. During a blood meal, an infected fly (day-biting flies) introduces third-stage filarial larvae onto the skin of the human host, where they penetrate into the bite wound. The larvae develop into adults that commonly reside in subcutaneous tissue . The female worms measure 40 to 70 mm in length and 0.5 mm in diameter, while the males measure 30 to 34 mm in length and 0.35 to 0.43 mm in diameter. Adults produce microfilariae measuring 250 to 300 μm by 6 to 8 μm, which are sheathed and have diurnal periodicity. Microfilariae have been recovered from spinal fluids, urine, and sputum. During the day they are found in peripheral blood, but during the noncirculation phase, they are found in the lungs . The fly ingests microfilariae during a blood meal . After ingestion, the microfilariae lose their sheaths and migrate from the fly's midgut through the hemocoel to the thoracic muscles of the arthropod . There the microfilariae develop into first-stage larvae and subsequently into third-stage infective larvae . The third-stage infective larvae migrate to the fly's proboscis and can infect another human when the fly takes a blood meal.

RNA Viruses

There are 13 families of RNA viruses (i.e more than DNA viruses) All RNA viruses replicate in the host cell cytoplasm except orthomyxo (e.g influenza) viruses (retroviruses in both the cytoplasm and nucleus) RNA of RNA viruses varies in its structure— ss or ds ssRNA is either positive (like mRNA) sense, negative sense Some may be segmented All negative sense RNA viruses are enveloped All negative sense RNA viruses carry an RNA dependent-RNA polymerase Only RNA viruses may be arthropod borne

Radiation

There are two types of radiation used in killing microbes- Ionizing and Non ionizing Ionizing radiation: X-rays, Gamma rays Have higher energy and greater penetrating power than ultraviolet light Create oxygen and hydrogen radicals from water Denature proteins and DNA Used to sterilize heat sensitive materials, such as gloves, syringes Non-ionizing radiation: UV light Destroy DNA by forming bonds between neighboring thymine molecule. Most lethal waves 240 nm-280 nm Poorly penetrate objects Used to sterilize air, operating theater (OT), surfaces Treatment of public water supply

Mutations in Bacteria

They reproduce fast, some divide within 20 min. Thus the probability of mutation is high. Because of their haploid state, bacterial mutations are expressed quickly, no recessive or dominant pattern Can occur as Spontaneous mutation: polymerase enzyme errors or Induced mutations: caused by mutagens - chemicals, radiation

Diagnosis of Babesia microti

Thin Smear: "Maltese cross" - intra-erythrocytic ring-shaped parasites in a thin blood smear. Inoculation of blood sample to hamsters Serology - IFA Detects Antibodies PCR

Strongyloides stercoralis

Threadworm First described in French troops stationed in modern day Vietnam during the late 19th century who were suffering from severe, persistent diarrhea. Epidemiology: Mostly tropical and subtropical climate and poor sanitation, warm moist soil. Sporadic cases in temperate regions 30-100 million infected persons worldwide; rural areas; often associated with agricultural activities. Transmission: penetration through the skin, similar to hook worm. Plus autoinfection Complicated life cycle - free living and parasitic form. Egg hatch into larva in the intestine. Mature larva (filariform) penetrate skin -goes through lungs - esophagus - intestine (like hookworm)

Viral Plaque Assay

Titration of Infectious Virus/ quantification of viral particles Cells lyse upon virus release Virus infects neighboring cells Clear zone is created as infection spreads outwards Clear zones are called plaques

Toxin mediated diseases

Toxin interrupt physiological functions. A. Mycotoxicoses: Results from ingestions of mycotoxins produced by fungi on food Ergot Alkaloids-by mold growing in grains (Claviceps purpurea) Causes ergotism- Hallucinations, GI-upset, dry gangrene and painful burning sensation: outbreaks Aflatoxin - produced by Apergillus flavus in moldy grains, peanuts carcinogenic toxin - induce mutation on p53 (growth suppressor gene) - causes liver cancer B. Mycetismus (Mycetism/Mushroom poisoning)results from eating poisonous mushrooms (Amanita spp) Amanitin/Phalloidin: Toxin resistant to heating - cooking does not inactivate May cause severe/fatal liver and kidney failure

Tissue Nematodes

Toxocara canis/ T. cati/Baylisarcaris procyonis - dogs/cat/racoon worms Ancylostoma caninum Dracunculus medinensis Filarial worms: Wuchereria bancrofti Brugia malayi Onchocerca volvulus Loa loa

Macromolecular Synthesis and Replication

Transcription of most viruses results in synthesis of early and late mRNA transcripts. The early transcripts encode regulatory proteins and enzymes required for DNA replication. This proteins are catalytic and only few are needed. The late transcripts encode mainly structural proteins of the virion. Replication of the genome usually initiates the transition to transcription of the late genes. Initiation of nucleic acid synthesis precedes transcription of the late genes.

Specialized Transduction

Transduction is transduction in which only certain donor genes can be transferred to the recipient. Different phages may transfer different genes but an individual phage can only transfer certain genes. Specialized transduction is mediated by lysogenic or temperate phage and the genes that get transferred will depend on where the prophage has inserted in the chromosome. During excision of the prophage, occasionally an error occurs where some of the host DNA is excised with the phage DNA. Only host DNA on either side of where the prophage has inserted can be transferred (i.e. specialized transduction). After replication and release of phage and infection of a recipient, lysogenization of recipient can occur resulting in the stable transfer of donor genes. The recipient will now have two copies of the gene(s) that were transferred. Legitimate recombination between the donor and recipient genes is also possible. Phage genome may pop out of chromosome with the exact genomic information it entered with - it is then non-transducing phage Phage genome may pop out of chromosome with a piece of bacterial chromosome which was adjacent to the insertion site - then it is a transducing phage. Since there is a size limitation on the amount of genomic material which can be packaged into a capsid, it must leave some of the original genome behind

Transduction

Transfer of bacterial genetic information using bacteriophage as the vehicle Bacteriophages Ds DNA viruses Complex structure, tadpole shaped-hexagonal head and cylindrical tail Head-icosahedral capsid with DNA 2 types: Virulent or lytic phage Temperate or lysogenic phage The phage coat protects the DNA in the environment so that transduction, unlike transformation, is not affected by nucleases in the environment. Not all phages can mediate transduction. In most cases gene transfer is between members of the same bacterial species. However, if a particular phage has a wide host range then transfer between species can occur. The ability of a phage to mediate transduction is related to the life cycle of the phage.

Generalized sequence of the stages of infection

Transmission from an external source into the portal of entry Evasion of primary host defenses such as skin or stomach acid Adherence to mucous membranes, usually by bacterial pili Colonization by growth of the bacteria at the site of adherence Disease symptoms caused by toxin production or invasion accompanied by inflammation Host response, both nonspecific and specific immunity, during steps 3,4 and 5 Progression or resolution of the disease

Treatment of Cyclospora cayetanensis

Trimethoprim/sulfamethoxazole Prevention and Control Increased sanitation and hygiene practices Warn travelers not to visit regions where the coccidian parasites are endemic Treatment with chlorine or iodine is unlikely to kill Cyclospora oocysts. No vaccine for cyclosporiasis is available

Epidemiology of Malaria

Tropical and subtropical, human to human via a vector- mosquito (Anopheles spp), by blood transfusions/organ transplant, also by IV drug use Malaria is one of the most severe public health problems worldwide. It is a leading cause of death and disease in many developing countries 1-5 billion febrile episodes and 1-3 million deaths annually. Approx. 1,500-2,000 cases every year in US Airport malaria: In Palm Beach County, Florida, during the summer of 2003, a cluster of eight cases of malaria was detected

Trypanosoma

Trypanosoma brucei 2 subclasses Trypanosoma brucei gambiense Trypanosoma brucei rhodesiense African Sleeping sickness Trypanosoma cruzi --American trypanosomiasis, Chagas disease

Reduviid bugs (Triatomine bugs/kissing bugs)

Trypanosoma cruzi vector, feeding and defecating on the wound after taking a blood meal. The bug excretes the trypomastigote form along its feces while feeding. It enters the bite site or eye while the persons rub the site of infection and the eye.

Oocysts of Cyclospora cayetanensis

Twice as large in comparison with C. parvum and are not sporulated (do not contain sporocysts) upon excretion

Fungal Diseases

Two categories: 1. Infectious : Mycosis (plural-Mycoses) 2. Non infectious most common site is the skin, - dermatophytes -candida

Treatment of Enterobiasis

Two doses of albendazole, mebendazole or pyrantel pamoate two weeks apart give a very high cure rate. The drugs are effective against adults The second dose is to kill new worms hatching from eggs (retroinfection) The entire family should be treated, to avoid reinfection. Bedding and underclothing must be sanitized between the two treatment doses Prevention and control Good personal hygiene; prompt Rx of infected persons

Metazoa (helminths)

Two groups 1. Platyhelminthes - flat worms: two forms- a) Cestodes: segmented body, (proglottids), no alimentary tract, head has suckers &/or hooks for attachment, hermaphroditic b) Trematodes: leaf shaped, oral/ventral suckers, blind alimentary tract, usually hermaphroditic 2. Nemathelminthes/Nematodes—round worms, long with true alimentary tract, oral attachment device possible, produce eggs/ larvae, separate sexes

Adherence

Two types: specific or nonspecific Specific: molecular recognition Duffy antigen is binding site for Plasmodium vivax Non specific: Mechanical "Hooks" in hookworms nonspecific

Hemagglutination Assay

Two-fold serial dilutions of a virus are prepared, mixed with a specific amount of red blood cells, and added to the wells of a plastic tray. The red blood cells that are not bound by the virus sink to the bottom. The red blood cells that are attached to virus particles form a lattice that coats the well Used to quantitate viruses that express hemagglutinins on their surface Reading (Example) Sample A: titer of 256 B: no virus detected D: titer of 512

Toxocara life cycle

Unembryonated eggs are shed in the feces of the definitive host . Eggs embryonate and become infective in the environment . Following ingestion by dogs, the infective eggs hatch and larvae penetrate the gut wall. In younger dogs, the larvae migrate through the lungs, bronchial tree, and esophagus; adult worms develop and oviposit in the small intestine (Similar to the route for Ascaris in humans). In older dogs, patent infections can also occur, but larval encystment in tissues is more common. Encysted stages are reactivated in female dogs during late pregnancy and infect by the transplacental and transmammary routes; the puppies in whose small intestine adult worms become established. Puppies are a major source of environmental egg contamination. Toxocara canis can also be transmitted through ingestion of paratenic hosts: eggs ingested by small mammals (e.g. rabbits) hatch and larvae penetrate and migrate into various tissues where they encyst . The life cycle is completed when dogs eat these hosts and the larvae develop into egg-laying adult worms in the small intestine. Humans are accidental hosts who become infected by ingesting infective eggs in contaminated soil or infected paratenic hosts . After ingestion, the eggs hatch and larvae penetrate the intestinal wall and are carried by the circulation to a wide variety of tissues (liver, heart, lungs, brain, muscle, eyes) . While the larvae do not undergo any further development in these sites, they can cause severe local reactions that are the basis of toxocariasis.

Translation in prokaryotes

Unique microbial initiation, elongation, and termination factors 1st aa - N-formyl methionine ( fMet) (soluble PAMP = recognized by innate immunity as foreign) Targeted by antimicrobial agents Eg, tetracyclines, Macrolides etc. Most metabolic regulatory mechanisms involve control of transcription of the gene into messenger RNA, rather than control of translation of the messenger.

Sterilization

Use of physical procedures or chemical agents to destroy all microbial forms, including the bacterial spores. Physical means: heat and radiation Mechanical means : filtration Chemical means: Alcohol, H2O2

Viral Evasion of the Immune Response

Various ways: few examples Existence in multiple Antigenic variants: eg. Influenza virus Latency- wait until the immune response weakens Infection of immuno-privileged sites within the body e.g. HSV in sensory ganglia in the CNS Interfere with antigen presentation Down regulation of MHC I expression, e.g. Adenoviruses Down regulation of LFA-3 and ICAM-1. Eg EBV LFA3: Lymphocyte function-associated antigen 3 (CD58): is a cell adhesion molecule expressed on Antigen Presenting Cells (APC), particularly macrophages. It binds to CD2 (LFA-2) on T cells and is important in strengthening the adhesion between the T cells and Professional APCs Inhibit TAP Transporter associated with Antigen Processing proteins Interfere with KAL and KAR i.e with NK recognition and killing, Eg. CMV Direct infection of the cells of the immune system, eg HIV

Detection of viral antigens

Viral antigens can be detected in the patient's blood or body fluids UV microscopy: by use of florescent dye tagged antibodies Serology: ELISA (Most common) Detection of p24 antigen of HIV, HBsAg of Hepatitis B Rapid tests Eg, for HBsAg of Hepatitis B

Pathogenicity Islands (PAIs)

Virulence cassettes: Unique area in the bacterial genomes where several genes are clustered, favoring their co-inheritance and co-expression May contain virulence genes Antibiotic resistance genes

Viral classification

Viruses are classified on the basis of their genome, capsid structure, envelope and replication strategy: Based on Genome: DNA: dsDNA; Gapped dsDNA; ssDNA; RNA: dsRNA; (+) ssRNA; (+) ssRNA with iDNA; (-) ssRNA. Based on Capsid Structure (capsid symmetry): Helical Icosahedral Complex Based on the presence/absence of Envelope Enveloped Non enveloped (naked)

Oncogenic human viruses

Viruses associated with human cancer

Naked viruses

Viruses that lack an envelope Naked with Icosahedral capsid: Capsomeres arranged in 20 triangles that form a symmetric figure - polyhedral e.g. poliovirus, adenovirus, hepatitis A virus Naked with Helical capsid: capsomeres arranged in a hollow coil that appear like a rod e.g. tobacco mosaic virus. So far no human viruses with this structure are known

Helix distortion mutations

When UV radiation induces dimerization of adjacent nucleotides, particularly thymines. Results cyclobutane ring in DNA, which prevents faithful replication

Complementation

When a defective virus is aided in its replication by a helper virus (complete virus/ or other defective virus) Can occur when either one or both of the two viruses that infect the cell have a mutation that results in a nonfunctional protein Non mutated virus (helper virus) complements the mutated one (defective virus) by making functional protein

Cyclospora cayetanensis : Life cycle

When freshly passed in stools, the oocyst is not infective (thus, direct fecal-oral transmission cannot occur; this differentiates Cyclospora from another important coccidian parasite, Cryptosporidium). In the environment , sporulation occurs after days or weeks at temperatures between 22°C to 32°C, resulting in division of the sporont into two sporocysts, each containing two elongate sporozoites . Fresh produce and water can serve as vehicles for transmission and the sporulated oocysts are ingested (in contaminated food or water) . The oocysts excyst in the gastrointestinal tract, freeing the sporozoites which invade the epithelial cells of the small intestine. Inside the cells they undergo asexual multiplication and sexual development to mature into oocysts, which will be shed in stools. The potential mechanisms of contamination of food and water are still under investigation.

Hfr Conjugation (Hfr × F-)

When the F factor integrates with the main chromosome 1.An F+ plasmid inserts into the donor bacterium's nucleoid to form an Hfr male. 2. The sex pilus adheres to an F- female (recipient). One donor DNA strand breaks in the middle of the inserted F+ plasmid. 3. The sex pilus retracts and a bridge forms between the two bacteria. One donor DNA strand begins to enter the recipient bacterium. The two cells break apart easily so the only a portion of the donor's DNA strand is usually transferred to the recipient bacterium. 4. The donor bacterium makes a complementary copy of the remaining DNA strand and remains an Hfr male. The recipient bacterium makes a complementary strand of the transferred donor DNA. 5. The donor DNA fragment undergoes genetic exchange (recombination) with the recipient bacterium's DNA. 6. The recipient bacterium gain new genes from the donor, but does not receive tra operon, thus remain F negative-.

Colony

a visible mass of microbial cells on solid/semisolid media that theoretically arose from one cell

Red man syndrome

in the past attributed to impurities found in vancomycin preparations, earning the drug the nickname 'Mississippi mud'. But reports of the syndrome persisted even after improvements in the compound's purity. Studies have shown that an unknown percentage of the population may be prone to releasing a large amount of histamine in response to vancomycin. The hypersensitivity reactions that can arise due to vancomycin are due to its effect on the mast cells. In tissue culture, vancomycin causes degranulation of peritoneal mast cells in rats. An anaphylactoid reaction (Vs. The anaphylactic reaction-which is mediated by IgE) is caused by the degranulation of mast cells and basophils, resulting in the release of histamine independent of preformed IgE or complement. The extent of histamine release is related partly to the amount and rate of the vancomycin infusion. The name comes from the red rash that develops on the face, neck, and torso (trunk) of affected people

Viral Genome

nucleic acid RNA or DNA (not both) Single (ss) or double-stranded (ds) Linear, circular ssRNA, either positive strand or negative strand RNA may be segmented Usually haploid, some diploid

Onchocerciasis

(River Blindness) Affects primarily, the eye, the skin, and lymph nodes Pathogenesis is mainly due to Direct invasion and immune reaction to migrating microfilariae (larva); Release of endotoxin like molecule by Wolbachia (rickettsia like bacteria as endosymbiont) Acute: fever, eosinophilia and urticaria Chronic: A. Ocular manifestation: microfilariae migrate to the surface of the cornea. Chronic infection leads to sclerosing keratitis - affected area becomes opaque. The entire cornea may become opaque = (River Blindness) B. Skin manifestations Nodules - known as Onchocercomata (contain - few adults) Intense itching, swelling, and inflammation. Scattered pruritic papules - small to large and may become keratinized Skin atrophy - loss of elasticity; thin and scaly skin - 'lizard skin' appearance Depigmentation - 'leopard skin' appearance, anterior lower leg. C. Hanging groin: lymph node enlargement and hanging down Mild to moderate lymphadenopathy particularly in inguinal and femoral areas where enlarged nodes may hang down in response to gravity due to loss of subcutaneous elastic fiber - "hanging groin''

Trichuris trichiura

(Whipworm) soil-transmitted helminths The adult worm measure 3-5 cm, resembles a whip-anterior three-fifth is very thin and hair like and the posterior two-fifth is thick and stout; resembling the lash and handle of a whip. The worm lives in large intestine Epidemiology: world wide Third most common roundworm of humans (worldwide) Southern United States Children at more risk Often seen in areas where human feces is used as fertilizer or where defecation onto soil happens No animal reservoir In the US: Whipworm infection in the rural Southeast, estimated 2.2 million people are infected･ Internationally: Whipworm infection is common in less-developed countries; more than 500 million people are infected worldwide Transmission: One of the soil transmitted helminths Fecal-oral

Uptake of mobile genetic elements

(phages, virulence plasmids and pathogenicity islands), as well as the loss of chromosomal-DNA regions in different E. coli lineages, has enabled the evolution of separate clones, which belong to different E. coli pathotypes and are associated with specific disease symptoms. LEE, locus of enterocyte effacement; PAI, pathogenicity island; pEAF, enteropathogenic E. coli adhesion-factor plasmid; pENT, enterotoxin-encoding plasmids; Stx, Shiga-toxin-encoding bacteriophage.

Protozoan Parasites

1. Amoeba (Sarcodina)—motile via pseudopods, divide by binary fission, exist as metabolically active trophozoites and inactive, resistant cysts. 2. Flagellates (Mastigophora)—motile via long whip-like flagellae, divide by binary fission, exist in trophozoite and cyst forms, exceptions exist 3. Ciliates (Cilliata)—motile via short, brush like cilia, divide by binary fission (may conjugate), exist as trophozoites and cysts 4. Sporozoa (Coccidia)—reproduce by sexual &/or asexual means, exist in diverse cellular forms, trophozoites, sporozoites, oocysts, gametocytes, etc. May be intracellular

Viral Isolation and Growth

1. Chicken eggs (Embryonated) - still used for some viruses 2. Animals - mainly for research purposes 3. Cell culture: Three types of cell lines: monolayer growth Primary cells - e.g. Monkey Kidney cells. These are essentially normal cells obtained from freshly killed adult animals. These cells have limited life span, and can only be passed (cultured) once or twice. Semi-continuous cells (diploid cell line)- e.g. Human embryonic kidney cells and skin fibroblasts. These are cells taken from embryonic tissue, and may be sub-cultured up to 50 times. Continuous cells - e.g. HeLa, Vero, Hep2, LLC-MK2, BGM. These are immortalized cells i.e. tumor cell lines and may be sub-cultured indefinitely.

Growth requirements for bacteria

1. Essential elements: Hydrogen, Oxygen, Carbon, Nitrogen, Phosphorus and Sulphur 2. Mineral sources: K, Mg, Fe, Cu, Co, Mn, Mb, Zn 3. Organic growth factors: Growth factors or bacterial vitamins May be essential or accessory Vitamins: thiamine, riboflavine, nicotinic acid, pyridoxine, folic acid and vitamin B-12

Phenol

1st disinfectant used rarely used, replaced by phenol derivatives Act by dissolving lipid solvents - disrupts cell membranes Effective disinfectants but too toxic for antisepsis Not sporicidal, not effective against non-enveloped viruses

Immunopathogenesis

1. Excessive immune response: innate, specific and inflammatory responses - Examples NK and CTLs - host cell death Activated neutrophils and macrophages: bystander damage Complement activation: anaphylatoxins, inflammation Granuloma formation: interfere with normal function 2. Molecular mimicry: Induction of autoimmune diseases: eg, M protein of Streptococcus pyogenes and heart protein (Rheumatic fever) 3. Immune complex deposition: In Bacterial endocarditis nephritis, arthritis, vasculitis

Anti-protozoal Drugs

1. Heavy metals: inhibits sylfhydryl group of enzymes and disrupt glycolysis Arsenicals: eg, Melarsoprol inhibits parasite pyruvate kinase (inactivates sulfhydryl groups) and causes decreased concentrations of ATP, pyruvate and phosphoenol pyruvate Antimonials: eg, Sodium stibogluconate 2. Inhibitors of DNA Replication Quinoline derivatives - Chloroquine, Primaquine Interfere with DNA replication and hemoglobin digestion Diamidines - Pentamidine: binds with DNA Nitroimidazoles - Metronidazole*- breaks DNA 3. Inhibitors of Folic Acid Biosynthesis: Inhibition of biosynthetic pathway Pyrimethamine inhibitis the enzyme dihydrofolate reductase (DHFR). Sulfonamides/Trimethoprim* 4. Inhibitor of pyruvate-ferridoxin oxidoreductase: Nitazoxanide: Inhibits anaerobic metabolism (protozoa and anaerobic bacteria) 5. Inhibitors of Protein Synthesis Paramomycins - Paramomycin (aminoglycoside) Tetracycline, clindamycin, spiramycin (macrolide) 6. Sesquiterpenes: Artemisinins, artemether React with heme moety causing free radical damage to parasite membranes Most effective antimalarial 7. Phosphocholine analogue: Miltefosine Act on key enzymes involved in metabolism of ether lipids present on the surface of parasite 8. Atovaquone-Proguanil (Malarone) Atovaquine inhibits electron transport chains of mitochondria of parasite Proguanil-antifolate (inhibits DHFR enzyme)

Mechanism of antibiotic resistance

1. Inactivation (cleavage) of antibiotics by enzymes 2. Active Efflux of drugs by membrane-bound multiple drug resistant (MDR) efflux pumps 3. Chemical Modification of the antibiotic: eg. transfer of acetyl group, methyl group 4. Decrease cell permeability of cell 5. Hyper-production of target 6. Mutation or post-translational modification of drug target 7. Formation of biofilm

Toxicara canis/cati and Baylisarcaris procyonis

1. Toxocara canis: Associated with Dogs 2. Toxocara catis: Associated with Cats 2. Balisarcaris procyonis: Associated with Racoons Toxocariasis: neglected parasitic infection in US (but, under CDC's priority), Almost 14% US people infected Baylisarcariasis: Fewer than 25 cases reported in US Dog, cat and raccoon parasites, humans accidently infected, humans are dead end host Risk group: Young children are at risk as they are more likely to put contaminated fingers, soil, or objects into their mouths. Transmission: Ingestion of eggs from dog/cat/racoon feces

Gene Transfer

1. Transformation: - the transfer of "naked" DNA. (DNA fragment and or plasmid) 2. Conjugation: the passage of plasmids/genetic elements through direct physical contact between two bacteria 3. Transduction: the transfer of genetic information through virus (phage). 4. Transposition: the movement of small pieces of DNA called transposons to different locations in the genome and between plasmids. These are sometimes called "jumping genes."

Environmental factors affecting growth

1. Water 2. Oxygen (obligate aerobes, microaerophiles, facultative anaerobes, aerotolerant anerobes and obligate anerobes) 3. Carbon dioxide 4. Temperature (Psychrophilic: below 20, meso-philic: 25-40, Thermophilic: 55-80 0 C) 5. Hydrogen ion concentration (optimal pH 7.2-7.4) 6. Light: Most prefer to grow in darkness except phototrophic 7. Osmotic pressure: Osmotically stabilized with 0.5% NaCl in growth media

Gas Pak system

A commercial product, available in the form of a disposable packet of aluminium foil containing pellets of sodium borohydride and cobalt chloride and of citric acid and sodium bi-carbonate, is now widely used for preparing anaerobic jars. The chemicals generate hydrogen and carbon di oxide inside the jar when water (10ml) is added. Hydrogen combines with Oxygen in the presence of a catalyst (eg. Alumina pellets coated with palladium) present in the undersurface of the lid of the jar. After the inoculated plates are placed inside a large air-tight jar, it is incubated at 370 C. The gas pak technique is simple and effective.

Rectal prolapse

A condition in which the lower portion of the colon, just inside the anal canal, becomes turned inside out and protrudes outside the body. In a whipworm infection, the rectum loses its internal support because the worms bury their thin heads into the intestinal lining, loosening the elastic epithelium and weakening the surrounding muscles. In addition to it, increased peristalsis in whip worm infection also contributes.

Zoonosis

A disease involving a parasite for which the normal host is an animal, and wherein man can also be infected Cryptosporidium, Trichinella etc are examples of zoonotic parasites that may be transmitted from animals to humans

Stool examination

A flotation media (for concentration) has a higher specific gravity than 1.20 to float many of the common parasite ova. Sheather's sugar solution has a specific gravity of 1.27 which is high enough to float any ova. Sedimentation use solutions of lower specific gravity Heavy eggs (Ascaris egg) Operculated eggs (Trematodes) Larvae (Strongyloides stercoralis) Cysts Floatation use a higher specific gravity than 1.20 Non Operculated eggs Trematodes (S. m.) Cestode Nematode(Hook worms) Cysts

Infrared combustion technology

A mobile thermal processing system that uses electrically-powered silicon carbide rods to heat organic wastes to combustion temperatures. Waste is fed into the primary chamber and exposed to infrared radiant heat (up to 1,850 °F) provided by silicon carbide rods above the conveyor belt. A blower delivers air to selected locations along the belt to control the oxidation rate of the waste feed. Any remaining combustibles are incinerated in an afterburner.

Suppression mutation

A mutation (second) that restores the function of a gene inactivated by previous mutation (first): Example ATA to AAA causes Tyr to Phe AAA to ATA causes Phe back to Tyr

Stages of Disease Progression

A primary infection refers to an infection you acquire for the first time A secondary infection is an infection that occurs during or after treatment of another pre-existing infection. It may result from the treatment itself or from changes in the immune system. For example, a vaginal yeast infection that occurs after antibiotic treatment of a bacterial infection is a secondary infection Types of infection: acute, chronic primary, secondary

Syncytia formation

A process wherein cells are caused by viruses to fuse together into giant cells. Multi-nucleated syncytial cells are often the result of infections by enveloped viruses that induce cell fusion.

Sigma Factor

A protein that associates with RNA polymerase that facilitates its binding to specific promoters a protein for initiation of RNA synthesis May associate with the RNA polymerase before binding to the promoter region or it may bind to promotor and act as a docking station for the polymerase. The specific sigma factor used to initiate transcription of a given gene will vary, depending on the gene and on the environmental signals needed to initiate transcription of that gene. Some sigma factors are inserted into the plasma membrane to "sense" the environment - may be targets for the adaptive immune system Turns on or off genes DNA- dep - RNA polymerase requires specific Sigma factors for accuracy and affinity of binding to the promoter New sigma factors allow new phenotypic expressions

One step viral growth curve

A single cycle of virus growth can be studied by determining the titer of infectious virus (e.g. by plaque assay) over time. Viral titer is stable during the brief period of virus attachment. Following attachment, viral titer declines precipitously as the virus undergoes disassembly, transcription, translation, and genome replication. That interval is termed the eclipse. Viral titer begins to increase as progeny virions, which are fully infectious, are assembled. Eclipse phase: corresponds to the period during which the input virus becomes uncoated. As a result, no infectious virus can detected during this time (any infectious virus detected is simply virus that is still stuck on the cell membrane) (Time period between entry and assembly/maturation) Latent period. During this period, no extracellular virus can be detected. (Time period between entry and release) Burst size : amount of infectious virus produced, per infected cell

Autoclave

A sophisticated pressure cooker. In its simplest form, it consists of a chamber in which the air can be replaced with pure saturated steam under pressure. Air is removed either by evacuation of the chamber before filling it with steam or by displacement through a valve at the bottom of the autoclave, which remains open until all air has drained out. The latter, which is termed a downward displacement autoclave, capitalizes on the heaviness of air compared with saturated steam. When the air has been removed, the temperature in the chamber is proportional to the pressure of the steam; autoclaves are usually operated at 121°C, which is achieved with a pressure of 15 pounds per square inch. Under these conditions, spores directly exposed are killed in less than 5 minutes, although the normal sterilization time is 10 to 15 minutes to account for variation in the ability of steam to penetrate different materials and to allow a wide margin of safety. The use of saturated steam in the autoclave has other advantages. Latent heat equivalent to 539 cal/g of condensed steam is immediately liberated on condensation on the cooler surfaces of the load to be sterilized. The temperature of the load is thus raised very rapidly to that of the steam. Condensation also permits rapid steam penetration of porous materials such as surgical drapes by producing a relative negative pressure at the surface, which allows more steam to enter immediately. Autoclaves can thus be used for sterilizing any materials that are not damaged by heat and moisture, such as heat-stable liquids, swabs, most instruments, culture media, and rubber gloves

Increase of antibiotic resistance

A. Increased use of antibiotics Selects for antibiotic resistance phenotypes. Administration of antibiotics without need 1/3 of outpatient prescriptions for antibiotics are unneeded Unregulated prescriptions Use of broad-spectrum antibiotics Use of antibiotics in agriculture Bystander effect on normal flora Serve as a link to pass on resistance genes When the antibiotics attack pathogenic (disease causing) bacteria, they also affect benign bacteria (innocent bystanders) in their path. They eliminate the drug susceptible bystanders that could otherwise limit the expansion of the pathogens and they simultaneously encourage the growth of resistant bystanders. Propagation of these resistant non pathogenic bacteria increases the reservoir of resistant traits in the bacterial population as a whole and raises the odds that such traits will spread to pathogens. In addition, sometimes the growing populations of bystanders themselves become agents of disease. B. Increased mobility of world's population C. Hospital setting: Selection and maintenance of antibiotic resistance genes

Diagnosis of Filarial Elephantiasis

A. Microscopy: demonstration larva (microfilariae) in Giemsa stained blood films (Blood collected at night) Buffy coat films Membrane filtration technique (blood mixed with saline and filtered) Differentiation between W. bancrofti and B. malayi is based on study of head and tail structure B. Serology: alternative to microscopy

Hyphal morphology (In molds)

A. Non septate or septate Non-septate or coenocytic : no separation of cells, mutinucleated Septate—cells separated by septa (cell wall) B. Dematiaceous (dark colored) or hyaline (colorless)

Pathogenesis of Strongyloides stercoralis

A. Skin manifestation: Ground itch - at site of penetration Migratory larva: Larva currens (Racing larvae), is a serpiginous (wavy) urticarial rash that creeps 5-15 cm/hr (i.e rapid migration) up the body B. Pulmonary manifestation: pneumonitis (Loeffler's synd.) migrating larvae- cough, dyspnea, wheezing, fever C. Intestinal manifestation: abdominal cramping, chronic bloody diarrhea, epigastric pain D. Hyper infection syndrome: autoinfection results recurring episodes for years, in immunocompromised pts. E. Disseminated strongyloidiasis: in immuncompromised pts (eg. AIDS). Any organ involvement- pulmonary, neurologic complications, shock, even death

Morphology of Naegleria fowleri

Amoeba - protozoan, exists as Cyst (only in the environment, not in human body) Trophozote (have pseudopodia, reproductive stage) Flagellated form

Hydatidosis

Abdominal cyst Treatment: Surgical excision-treatment of choice; If inoperable, high dose albindazole or praziquantel Prevention: Health education regarding the transmission of the parasite

Pathogenicity

Ability to cause disease

Types of viral infection

Abortive: in non-permissive cells; replication does not occurNon permissive cell: may lack a receptor, important enzyme pathway, transcriptional activator or express an antiviral mechanism that will not allow replication of the virus Viral mutants, which cause abortive infections, do not multiply and disappear. In-apparent: little to no damage or rapid resolution eg. Cytomegalovirus in healthy Acute/Lytic : in permissive cells: host cell death - eg. Adenovirus Persistent: starts with acute phase, remain long A. Chronic (productive): Hepatitis B virus B. Latent (limited viral macromolecular but no virus synthesis): eg, Herpes virus C. Recurrent (periods of latency then virus production): eg, Herpes virus D. Transforming- Immortalization - oncogenesis - oncogenic virus eg. Papillomavirus

Non-Gram-staining bacterium

Acid Fast: Mycobacterium Cell wall less: Mycoplasma Atypical cell wall: Chlamydia, Chlamydophila, Orientia, Ehrlichia and Anaplasma, Rickettsia Spirochetes: Treponema Borrelia Leptospira

Trichinella spiralis: Life cycle

Acquired by ingesting meat containing cysts (encysted larvae) of Trichinella. After exposure to gastric acid and pepsin, the larvae are released from the cysts and invade the small bowel mucosa where they develop into adult worms (female 2.2 mm in length, males 1.2 mm; life span in the small bowel: 4 weeks). After 1 week, the females release larvae that migrate to the striated muscles where they encyst . Trichinella pseudospiralis, however, does not encyst. Encystment is completed in 4 to 5 weeks and the encysted larvae may remain viable for several years. Ingestion of the encysted larvae perpetuates the cycle. Rats and rodents are primarily responsible for maintaining the endemicity of this infection. Carnivorous/omnivorous animals, such as pigs or bears, feed on infected rodents or meat from other animals. Different animal hosts are implicated in the life cycle of the different species of Trichinella. Humans are accidentally infected when eating improperly processed meat of these carnivorous animals (or eating food contaminated with such meat).

Sulfonamide and Trimethoprim

Act in the same pathway toward the synthesis of folic acid and eventually to purines and DNA. Sulfonamides are structural analogue to PABA. Sulfas mimic para-aminobenzoic acid needed by bacteria for folic acid synthesis. Sulfas inhibit bacterial folic acid synthesis at the level of the enzyme dihydropteroate synthetase Trimethoprim impairs folic acid synthesis at the level of dihydrofolate reductase. Human cells are not affected by these drugs, because unlike bacterial cell human cells require preformed folic acid Pharmacology: Usually used together Broad spectrum Bacteriostatic Urinary tract infections Gastrointestinal tract infections Respiratory infections Mechanisms of Resistance Efflux pumps are proteinaceous transporters localized in the cytoplasmic membrane of all kinds of cells. Alteration (mutation) of enzymes dihydropteroate synthetase and dihydrofolate reductase Overproduction of PABA and or dihydrofolic acid Many bacteria, including those found in the human intestinal tract such as E. coli, generate PABA from chorismate, a biochemical intermediate. Folic acid dependency Decreased permeability

Innate Response Against Viruses

Activation of NK cells Infected cells produce interferon 1 Dendritic cells/macrophages produce IL-12, TNF alpha, etc. Toll like receptors TLR3 and TLR7, TLR8 found in NK cells: recognize viral PAMP These lead to activation of NK: which in turn results in -Killing of infected cells -Production of interferon gamma and IL-12 -favouring the development of Th1 (promote cell mediated immunity) -activation of CD8 and macrophages. Once NK are activated by either by IFN alpha/beta, IL-12, TNF alpha or by binding ssDNA/dsRNA through TLR3/TLR7/TLR8, they produce Interferon gamma which favour the development of Th1 and also activates CD8 and macrophages.

Rhodesian sleeping sickness (East ASS)

Acute phase occurs very rapidly-fever, rigors, myalgia Lymphadenopathy Progresses to a fulminating, rapidly fatal illness CNS invasion early (within few wks)-lethargy, anorexia, mental disturbance, neurological problems Kidney damage, myocarditis and death

Pathogenesis of Schistosomiasis

Acute phase; Swimmer's itch: within 12 hrs, common with non human schistosomes. immune reaction to penetrating cercariae (Type I HSR); Katayama fever: 2-3 weeks, onset of oviposition results in fever, chills, cough, urticaria, arthralgia, splenomegaly and abdominal pain Chronic phase: Presence of eggs; formation of granuloma as well as production of proteolytic enzymes by the eggs Mostly affected organs are the liver, spleen, wall of the gut or bladder. Eggs may enter blood and get deposited in any other organ such as brain, heart Eggs in the liver: periportal fibrosis and portal hypertension resulting in hepatomegaly, splenomegaly and ascites In the bladder: granulomatous lesions, hematuria and sometimes urethral occlusion. bladder cancers In the intestine: cause polyp formation which, in severe cases, may result in life threatening dysentery.

Pathogenesis of trichinosis

Adult lives in intestine, larvae in muscles in the same host Toxic secretions by migrating larvae-vasculitis Host reaction to large numbers of larvae and their metabolites in vital muscles The larvae promotes formation of collagenous capsule- Nurse cell The muscle fibers become enlarged, edematous and deformed. The paralyzed muscles are infiltrated with neutrophil, eosinophils and lymphocytes. Splinter hemorrhage beneath the nails: due to vasculitis resulting from toxic secretions of the migrating larvae

Pathogenesis of Taenia solium

Adult lives in the intestine, larvae can be found in many parts of the body Clinical Disease: Taeniasis Intestinal taeniasis: most infections are asymptomatic, mild abdominal discomfort. Cysticercosis: Associated with ingestion of eggs (through contaminated water or vegetations/salad). Cyst (cysticercus i.e larval stage) in tissue: Space occupying lesion. Immune response when the cyst dies; may calcify Symptoms depends on the tissue affected. In brain (NCC)- results in seizures, headaches, and vomiting. In Spinal cord - paralysis, In eyes - blindness

Pathogenesis of Scabies

Adult mites enter the skin, produce eggs-develop into larva and nymph stages Embedded in the stratum corneum Presence of mites and their feces/secretions cause type IV hypersensitivity reaction and intense itching Scabies/Mange/Itch Intense itching; short, slightly raised burrows; worsening at night Interdigital and popliteal folds, wrist, inguinal region, along belt line Occasionally, excoriation, crusts and secondary bacterial infection In immunodeficient people: more severe form-Norwegian scabies-generalized dermatitis with extensive scaling and crusting and presence of thousands of mites in the epidermis

Pathogenesis of Paragonimus westermani

Adult worm commonly lives in the lungs Pulmonary: asymptomatic to severe tuberculosis like/ chronic pneumonia Long term - pulmonary fibrosis, pleurisy: pulmonary pain, chronic bad/dry cough, bronchitis, blood in the sputum/rusty brown sputum. Extra-pulmonary: brain, spinal cord, intestinal wall etc

Ascaris lumbricoides: Life cycle

Adult worms live in the lumen of the small intestine. A female may produce approximately 200,000 eggs per day, which are passed with the feces. Unfertilized eggs may be ingested but are not infective. Fertile eggs embryonate and become infective after 18 days to several weeks , depending on the environmental conditions (optimum: moist, warm, shaded soil). After infective eggs are swallowed, the larvae hatch, invade the intestinal mucosa, and are carried via the portal, then systemic circulation to the lungs. The larvae mature further in the lungs (10 to 14 days), penetrate the alveolar walls, ascend the bronchial tree to the throat, and are swallowed . Upon reaching the small intestine, they develop into adult worms. Between 2 and 3 months are required from ingestion of the infective eggs to oviposition by the adult female. Adult worms can live 1 to 2 years. Geographic Distribution: The most common human helminthic infection worldwide. Highest prevalence in tropical and subtropical regions, and areas with inadequate sanitation. Occurs in rural areas of the southeastern United States.

Pathogenesis of Loiasis

Adults live and migrate through the subcutaneous tissue, muscles, and in front of the eye Clinical manifestations: Skin: Calabar/fugitive swelling. When the worms migrate through subcutaneous tissues, they create pruritic nodules as a result from allergic reaction. Transient, common in extremities, 5 to 10 cm in diameter Eye: Eyeworm: migration of worm under the conjunctiva- irritation, painful congestion, edema of eye lids; (loss of vision-rare)

Pathogenesis of Clonorchis sinensis

Adults live in the bile duct causing inflammation resulting in fibrosis and hyperplasia, narrowing or blockage of the bile ducts. In heavy infection eggs may enter the liver causing granuloma. Association with gall-bladder stone formation (picture-next slide) Clinical disease: Indigestion, epigastric discomfort, weakness and loss of weight. Heavy infections: liver enlargement, Chole-cystolithiasis, jaundice, edema, ascites and diarrhea.

Schistosoma spp. and habitat in humans

Adults live in urinary or mesenteric (i.e GIT) blood vessels, life expectancy, 10 to 25 years Three spp: Schistosoma mansoni, Schistosoma japonicum Live in mesenteric blood vessels of human and baboons, domestic animals, rodents Schistosoma haematobium - lives in veins draining the urinary bladder (Venous plexus of bladder), human is the only host

Hookworm morphology

Adults: Male and Female separate, ≈1cm. ♀is slightly larger than♂ Male's posterior end is expanded in an umbrella like fashion to form a copulatory bursa. Larvae: Rhabditiform and filariform Eggs: 60×40 µm, oval in shape, shell is thin and colorless (not bile stained), contains a segmented ovum, usually with 4 blastomeres, clear space between the egg shell and segmented ovum

Enterobius vermicularis: Life cycle

After ingestion the embryonic eggs (i.e, with larvae), they hatch in the duodenum and reach adolescence in jejunum and upper ileum. Adult worms descend into lower ileum, cecum and colon and live there for 7 to 8 weeks. After mating the male dies. The gravid females, containing more than 10,000 eggs migrate, at night, to the perianal region and deposit their eggs there. It then secretes a substance that causes a very strong itching sensation, inciting the host to scratch the area and thus transfer some of the eggs to the fingers. Eggs mature in an oxygenated, moist environment and are infectious 3 to 4 hours later. The eggs can be found in underclothes, bedding material, they can be carried in the air and contaminate any other house holds, such as curtains, floors. The eggs can survive from 2 to 3 weeks on their own outside of the human body Retro-infection can also occur, that is the migration of newly hatched larvae from the anal skin back into the rectum Reported up to 1000 females on the scotch tape + 50000 eggs Female goes out at night to the oxygenate environment to release her eggs. Diagnosis under microscope looking at the eggs (Asymmetrical in shape (plano-convex)

Multi-site mutations

Also known as Macrolesion. Alteration of DNA involving large no. of base pairs, More comprehensive changes in the DNA, involve loss (deletion), gain (addition), duplication or inversions

Phase variation (conversion)

Also known as programmed gene rearrangement Switch genes on/off: results in phenotype switching that is faster than mutation Transcriptional regulation of alternative genes. This is not mutation: no gene is changed, Only the direction of the promoter or position of a gene is changed. There are several ways this is achieved The changes may affect host cell binding and virulence Eg. Pili of Neisseria gonorrheae Several genes encoding proteins with the same or similar functions and the ability to express only one of the these genes at a time. In effect this is achieved by maintaining only one active promoter at a time and/or moving genes to a position downstream of an active promoter.

Dermatophytide

An allergic rash caused by an inflammatory fungal infection (tinea) at a distant site. The rash is usually itchy like dermatitis, with bumps or blisters scattered on face, trunk and/or limbs.

Vector

An arthropod or other living carrier that transports a pathogenic organism from an infected to a non-infected host. Mechanical vectors: are non essential to the life cycle of the pathogen Biological vectors: serve as the site of some developmental events in the life cycle of the parasite

Trypanosoma cruzi Life Cycle

An infected triatomine insect vector (or "kissing" bug) takes a blood meal and releases trypomastigotes in its feces near the site of the bite wound. Trypomastigotes enter the host through the wound or through intact mucosal membranes, such as the conjunctiva. Common triatomine vector species for trypanosomiasis belong to the genera Triatoma, Rhodnius, and Panstrongylus. Inside the host, the trypomastigotes invade cells near the site of inoculation, where they differentiate into intracellular amastigotes . The amastigotes multiply by binary fission and differentiate into trypomastigotes, and then are released into the circulation as bloodstream trypomastigotes . Trypomastigotes infect cells from a variety of tissues and transform into intracellular amastigotes in new infection sites. Clinical manifestations can result from this infective cycle. The bloodstream trypomastigotes do not replicate (different from the African trypanosomes). Replication resumes only when the parasites enter another cell or are ingested by another vector. The "kissing" bug becomes infected by feeding on human or animal blood that contains circulating parasites . The ingested trypomastigotes transform into epimastigotes in the vector's midgut . The parasites multiply in the midgut and differentiate into infective metacyclic trypomastigotes in the hindgut . Trypanosoma cruzi can also be transmitted through blood transfusions, organ transplantation, transplacentally, and also by laboratory accidents.

Molecular Version of Koch's Postulates

An organism under investigation should be a member of pathogenic strains; and gene in question should be found in all pathogenic strains but absent from nonpathogenic strains The gene(s) coding for the responsible virulence factor(s) must be expressed during infection Inactivation of the gene (s) associated with virulence should lead to measurable decrease in pathogenicity Reversion of the inactivated gene/s should lead to restoration of pathogenicity. originally described by Dr.Stanley Falkow

Ancylostoma caninum & braziliense

Ancylostoma caninum : dog hookworm Ancylostoma braziliense: cat hookworm Larva can penetrate human skin, migrate under the skin, but does not complete its life cycle - human is a dead end host Children (exposure to soil contaminated with dogs and cat feces) are at risk In humans they cause severe erythematous and vesicular reactions- cutaneous larva migrans (CLM)literally means "wandering larvae in the skin", creeping eruption or ground itch (Differentiation from Larva currens- plz. see note) With A. brazilense- migration through lungs causes transient pulmonary infiltrates with peripheral eosinophilia (Loeffler's syndrome)

Cell Wall Synthesis Inhibitors

Beta Lactams -Penicillins -Cephalosporins -Carbapenems -Beta Lactamase Inhibitors: are structural analogues of penicillins/cephalosporins and have little antibacterial activity but bind strongly to beta lactamases thus protect penicillins/cephalosporins. Vancomycin Bacitracin For t/t of mycobacterial infection Cycloserine Isoniazid (INH) Ethionamide Ethambutol Pyrazinamide

Evasion of immune system

Antigenic variation - within one life stage or due to different life stages (eg, African trypanosomiasis, Plasmodium, Babesia spp, Giardia) Encystation - uses the host response to wall itself off Antigenic mimicry: eg, Plasmodium spp, Trypanosomes, Schistosomes Antigen masking: Shistosoma mansoni Antigen shedding: Trichinella Masking/camoflage - uses discarded host antigens to hide by pasting them to their surface or molecular mimicry (eg, Hydatid cyst, filaria, Trypanosomes) Intracellular location Ig and/or complement proteases some produce DAF like molecule and destabilize C3b, others bind to C9 and prevent it from forming MAC (eg. Protease by Malarial parasite) Immunosuppression - diversion of the host immune response to ineffective immune response: Extracellular developmental stage secretes chemicals that down regulate a humoral (Th2) immune response Intracellular developmental stage secretes chemicals that down regulate a cell mediated (Th1) immune response Others suppress the immune system by producing antioxidant - interfere with macrophage killing

Assembly and Release

Assembly The site of assembly depends on the site of replication of genome Assembly can be in the nucleus or cytoplasm Nucleocapsid assembly Procapsid formation - empty capsid proteins assemble first then gets filled with the genome OR, Capsid proteins assemble around the genome. Release Naked viruses: released by cell lysis or exocytosis Enveloped viruses: Viral proteins are delivered to cellular membranes. Nucleocapsid moves underneath the membranes (nuclear, golgi, or cell membrane) with viral proteins; and leave by budding.

Categories of Infectious Agents

Bacteria - Prokaryotes, unicellular Virus - acellular, has either DNA or RNA Fungi - eukaryotes, unicellular/multicellular Parasites - eukaryotes, unicellular/multicellular Prions - abnormal proteins/ proteinaceous infectious agents, no nucleic acid

Types of Culture Media

Basal (Simple) Media: contains peptone, meat extract, NaCl & H20 eg., Nutrient agar Enriched Media: contains additional substances like in blood, serum, eggs or extracts from animal tissue that encourage the growth of organism eg, Blood agar, Chocolate agar Selective media: allows growth of only the desired microbes. The purpose is to inhibit the growth of unwanted organisms eg, LJ medium for M. tuberculosis Enrichment media: purpose same as selective media but liquid eg, Selenite F broth for Shigella Differential Media: are used to distinguish among different organisms eg. MacConkey agar, EMB agar Transport media: eg. Stuart's medium for Gonococci

Nutritional classification of bacteria

Based on their energy requirements and on their ability to synthesize essential elements Autotrophs: can synthesize all their organic compounds Photo-autotrophs: derive their energy from sunlight Chemo-autotrophs: obtain their energy from chemical reactions Heterotrophs: Unable to synthesize their own metabolites and depend on preformed organic compounds Majority of the pathogenic bacteria are heterotrophs

Bacterial Cell Morphology

Basically there are three shapes Rods/bacilli (Coccobacilli) Cocci Spiral (spirochete, spirilla) Some show variation of these three basic structures Most bacteria are monomorphic Few are pleomorphic (many-shaped)

Chlamydoconidia

Become larger than the hypha, are round and thick-walled , borne usually on the terminal end of the hyphae or along side.

Taenia saginata

Beef Tapeworm Epidemiology: worldwide; one of most frequent causes of cestode infections in US; intermediate host-cattle; human- definitive host Transmission: eating undercooked or raw beef (containing larval form i.e. cysticercus) Pathogenesis: infects intestines, mechanical obstruction, sharing food. (No cysticercus in human tissue) Clinical Disease: Taeniasis; most infections are asymptomatic, can cause mild vague abdominal discomfort Annoyance - passive passage of 1-6 proglottids Length of adult worms is usually 5 m or less for T. saginata (however, it may reach up to 25 m) and 2 to 7 m for T. solium

Antihelminthic transport disruption

Benzimidazole - Mebendazole, Albendazole Broad spectrum anthelmintic Multiple paths: inhibits glucose transport and fumarate reductase, disrupts microtubules

Penicillin resistance

Beta-lactamase production: Genes carried on plasmids : spread easily Betalactamase activity: have various degree of spectrum Penicillinase : inactivates penicillins Cephalosporinase: Inactivates cephalosporins, Extended-spectrum batalactamase (ESBL); inactivates both drugs (P+C) Carbapenemase: against Penicillins + Cephalosporins + Carbapenems + Monobactems Alteration of Penicillin Binding Protein (form PBP 2A) Eg. By Methicillin resistant Staphylococcus aureus (MRSA) (mec A gene mediated: alter target)

Penicillin

Betalactam Antibiotic Structure: Nucleus: 6-Aminopenicillanic Acid Beta Lactam Ring Thiazolidine Ring (5 membered) R group R group altered in Semisynthetic Penicillins Access of beta lactamase enzyme to the beta lactam ring of semisynthetic penicillin is blocked by modification of the side chain with the addition of large aromatic rings, containing bulky methyl or ethyl groups.

Tegument

Between capsid and envelope-containing viral proteins and enzymes for replication

Adhesion Factors

Binding specific molecules on host cells Determines tissue/ host specificity Pili, capsule, biofilm Cell wall structure: lipoteichoic acid Proteins on the cell wall Eg. Escherichia coli - urinary tract infection - has P fimbriae binds to Gal-Gal dimer on P antigen found on uroepithelial cells F protein found on cell wall of Streptococcus pyogenes - binds to fibronectin

Bacterial Classification

Binomial nomenclature: Genus and species: Staphylococcus aureus Classification/taxonomy: based on- Phenotype: based on morphology, staining properties, biochemical properties (biotyping), Genetics: DNA studies Antigenic variation: serotyping Phage typing : Sensitivity to bacteriophage

Treatment of Fasciola hepatica

Bithionol is a chlorinated bis-phenol. It is suggested that bithionol is an uncoupler of oxidative phosphorylation. It has anthelmintic properties and is active against the trematodes Fasciola hepatica (sheep liver fluke) and Paragonimus westermani (lung fluke). Triclabendazole broad spectrum anthelmintic agent Prevention and control: Same as F. buski

Schistosoma spp.

Blood flukes Schistosomiasis Bilharziasis Snail fever The disease is often associated with water resource development projects, such as dams and irrigation schemes, where the snails, intermediate hosts of the parasite, breed. Has low mortality but high morbidity rate. Epidemiology: World wide; affecting millions (approx.250), 2nd most prevalent tropical disease (after malaria) often associated with water resource development projects, such as dams and irrigation schemes; Transmission- skin penetration by cercaria (larva) : Eggs, larvae (various stages) and adults Adults: The sexes are separate, the male and female live attached to each other. This ensures fertilization

Microscopy of Malaria

Blood smear (thick/thin) examination after Giemsa staining-infected red blood cells, ring form, and gametocyte form. P. falciparum, can be differentiated from the others by multiple ring form per cell and crescent shaped gametocyte Thick films contain 10 to 20 times more blood than thin films, correspondingly providing increased sensitivity for malaria screening

Variations of Microscopes

Bright-field (eg, Compound microscope)- most widely used; specimen is darker than surrounding field; best for preserved and stained specimens Dark-field - brightly illuminated specimens surrounded by dark field; used to detect live and unstained specimens - mostly for spirochetes Phase contrast : Uses parallel beam of lights which passes through objects of different densities. The wavelength of one beam moves out of 'phase' relative to other beam of light. Used for detailed analysis of internal structure in living cells UV/ Fluorescent microscope: uses ultraviolet light and fluorescent compounds - mostly for immunofluorescent (eg. DFA) stained smear - for fast diagnosis Such as CSF, Tissue biopsy, culture isolate Electron microscope: uses beams of electrons - mostly used for viruses, Types- Scanning and Transmission EM

Vegetative reproduction

Budding: Budding by constrictions results in Blastospores (Blastoconidia) If cells do not separate, they form pseudohyphae Fragmentation of hyphae: results in Arthrospores (Arthroconidia)

Treatment of Brown Recluse Bite

Cleansing bite wounds, tetanus prophylaxis and antibiotics for prevention of secondary bacterial infection Antivenom within 24 hours (early administration has better result) Prevention and Control: Similar to Black Widow Spiders

Plasmodium spp.

Causes Malaria Five species of medical importance P. falciparum (most serious form of malaria) P. vivax P. malariae P. ovale P. knowlesi: Infects primarily long-tailed & pig-tailed macaques human cases in Malaysia & other South east Asian countries)

Mechanisms of viral transformation

Cell growth is controlled by the maintenance of a balance in the external and internal growth activators (accelerators) and by growth suppressors, such as p53 and the retinoblastoma (RB) gene product (brakes). Oncogenic viruses alter the balance by removing the brakes or by enhancing the effects of the accelerators.

Adaptive Response Against Viruses

Cell-mediated: CD4 Th1 and CD8 Tc: killing infected cells, targets the intracellular phase of the virus Humoral immunity: primarily targets extracellular phase/cell surface expressed antigen Antibodies against viral attachment proteins (VAP): prevent infection Opsonization complement activation by antibody against virus Elimination via ADCC by NK cells (Ab provides specificity) Neutralization: Prevents spread by blocking extracellular virus particles

Point mutations

Change in single nucleotide Base pair substitution (Transition-most frequent, Transversion) Silent mutation: does not produce obvious effect Also called microlesion, changes in single nucleotides, may not necessarily result in detectable change in protein synthesis. Generally reversible. Two classes: I. Base pair substitution: Single base pair is substituted for another pair Transition-Substitution of one base pair but the purine, pyrimidine orientation is preserved. Happen by replacement of one pyrimidine by another pyrimidine, and one purine by another purine. Most frequent type of mutation Transversion: Pyrimidine is replaced by purine and vice versa, less frequently observed II. Silent mutation: It is a change at the DNA level only that does not result in any change of amino acid in the encoded protein. This is because more than one codon may encode an amino acid eg. GGT to GGA still gives proline.

Clonorchis sinensis

Chinese or Oriental liver fluke/Opisthorchis sinensis Epidemiology: oriental region, one of the most frequent infection seen among Asian refugees, fresh water fish and snail- intermediate hosts; Dogs, cats and fish eating mammals as reservoir hosts Transmission : eating raw freshwater fish, undercooked fish Morphology Egg Larva: various stages Adult

Pathogenesis of Cystoisospora belli

Clinical disease: Asymptomatic or mild to severe GI disease (similar to Giardiasis); malabsorption Watery diarrhea with foul smelling stools

Pathogenesis of Trichomonas vaginalis

Clinical disease: Trichomoniasis - more common in female Female- found in urethra and vagina, male- in urethra and prostrate gland Female: Inflammation of the vagina and cervix with itching and burning. Vaginal discharge which is scant, frothy, greenish-yellowish Strawberry red cervix Males: usually asymptomatic as reservoir May cause urethritis with discharge

Molecular fungal diagnosis

Clinical sample: PCR: Amplification of Fungal DNA In situ hybridization: detection of fungal DNA in tissue biopsy Culture: use of DNA probes to identify fugal culture; PCR

Operons

Clusters of co-regulated genes: with a promoter, operator and structural genes These genes are regulated such that they are all turned on or off together. Grouping related genes under a common control mechanism allows bacteria to rapidly adapt to changes in the environment. Prokaryotic genes to be regulated in the same manner are grouped together in operons, under the control of a single promoter and operator. Transcription of an operon is dependent upon whether or not the repressor (encoded by a nearby gene) binds to the operator region. Inducible or Repressible

Inclusion bodies

Collections of replicating virus particles either in the nucleus or cytoplasm: Have diagnostic importance Examples of inclusion bodies include the negri bodies and cytomegalic inclusion bodies found in rabies and CMV infections respectively.

Virus

Comes from the Latin word for "poison" Submicroscopic - measured in nm - electron microcopy Acellular - inert, not considered to be "living" Incapable of self-replication They are obligate intracellular infectious agent Must encode any required processes not provided by the host cell Replicate by assembly of individual components within host cell 1890s - First identified as filterable infectious agents (passed through filters that removed bacteria) - It was suggested that the infection might be caused by a toxin produced by bacteria (The agent is now known as tobacco mosaic virus) 1901 - first human virus discovered - Yellow Fever Virus 1909 - poliovirus, 1933 - influenza virus, 1963-hepatitis B virus

Pili (Fimbrae)

Commonly on Gram Negatives For adhesion and/or transport of bacterial material (sex pili) Fimbrins, adhesins, pilins - capable of inducing a specific immune response Adhesins in pili may be species specific and some are capable of undergoing antigenic variation; avoid immune response and/or bind to different host cells Bacteria are constantly losing and reforming pili as they grow in the body and the same bacterium may switch the adhesive tips of the pili in order to adhere to different types of cells and evade immune defenses

Protoplast

Complete Removal of the cell wall of a Gram positive bacteria results in the formation of protoplasts, which lyses unless it is osmotically stabilized

Smallpox (Variola) virus

Complex Structure Ds DNA, enveloped Complex appearance: brick like external structure and complex internal structure

Gram Negative Cell Wall

Components: Outer membrane: Phospholipid bilayer Lipopolysaccharide ( LPS) Porins proteins Lipoprotein Thin layer of peptidoglycan Periplasmic space: contain enzymes, such as nutrient transport enzymes

Gram Positive Cell wall

Components: Thick multilayered peptidoglycan Teichoic acids (TA) Lipoteichoic acids (LTA) Pentaglycine aa bridge cross -linking of peptidoglycan layers Teichoic acid and lipoteichoic acid. (water soluble polymers that contain ribitol or glyceral phosphate) These are species specific; some may be conserved across a genus. They are immunogenic and trigger a specific immune response but they may also undergo antigenic variation.

Fungal cell wall

Composed of Chitin,Glucan, Mannan and proteins Chitin: a polymer of N acetylglucosamine (provides rigidity) Major composition of fungal cell wall Glucan : a polymer of D-glucose - provide additional strength Mannan +protein: a polymer of the mannose sugar found linked to surface protein. May undergo antigenic variation, activate complement Glucan and Mannan = PAMP (induce innate immunity)

Bacterial growth curve

Consists of the following phases: I. Lag phase: No appreciable multiplication of cells although they may increase considerably in size and show marked metabolic activity (total count remains same) This initial period is the time required for adaptation to the new environment during which necessary enzymes and metabolic intermediates are built up in adequate quantities for multiplication to proceed II. Log or exponential phase: Cells start dividing by binary fission and their number increase exponentially or by geometric progression with time Linear relationship between time and the logarithm of no. of cells Cells at this phase are smaller and stain uniformly Many antibiotics are effective at this stage III. Stationary phase: Cell division comes to halt due to depletion of nutrients and accumulation of toxic products The no. of progeny cells formed is just enough to replace the no. of cells that die Viable count remains stationary (However, total count is more) Cells are Gram variable and show irregular staining Sporulation occurs at this stage Also, many bacteria may produce exotoxins. IV. Phase of decline: Decrease in population due to death of cells Cause may be: nutritional exhaustion, toxic accumulation, action of autolytic enzymes etc. Involution forms (irregular, atypical form) are common

Pathogenesis of Dracunculiasis

Creation of vesicles and ulcers in the skin (Most commonly lower body parts; Also seen in arms, trunk, buttock, scrotum, head, neck and female breast) Site of ulceration-erythema, pain and allergic reaction Complications: Abscess formation and secondary bacterial infection Resulting in tissue destruction and sloughing of skin Generalized infection (sepsis) Joint infections (septic arthritis) that can cause the joints to lock and deform (contractures) At the site where worm dies- calcification and nodule formation

Entamoeba histolytica: life cycle

Cysts and trophozoites are passed in feces . Cysts are typically found in formed stool, whereas trophozoites are typically found in diarrheal stool. Infection by Entamoeba histolytica occurs by ingestion of mature cysts in fecally contaminated food, water, or hands. Excystation occurs in the small intestine and trophozoites are released, which migrate to the large intestine. The trophozoites multiply by binary fission and produce cysts, and both stages are passed in the feces. Because of the protection conferred by their walls, the cysts can survive days to weeks in the external environment and are responsible for transmission. Trophozoites passed in the stool are rapidly destroyed once outside the body, and if ingested would not survive exposure to the gastric environment. In many cases, the trophozoites remain confined to the intestinal lumen (: noninvasive infection) of individuals who are asymptomatic carriers, passing cysts in their stool. In some patients the trophozoites invade the intestinal mucosa (: intestinal disease), or, through the bloodstream, extraintestinal sites such as the liver, brain, and lungs (: extraintestinal disease), with resultant pathologic manifestations. It has been established that the invasive and noninvasive forms represent two separate species, respectively E. histolytica and E. dispar. These two species are morphologically indistinguishable unless E. histolytica is observed with ingested red blood cells (erythrophagocystosis). Transmission can also occur through exposure to fecal matter during sexual contact.

Diagnosis of trichinosis

Demonstration of encysted worms (larvae) in muscle on biopsy, Serology Complement fixation, Bentonite flocculation test etc. Marked eosinophilia

Diagnosis of Fasciolopsis buski

Demonstration of large, golden, bile stained eggs with operculum (in stool)

Diagnosis of Ancylostoma caninum & braziliense

Demonstration of larvae in skin biopsy Along with clinical appearance of tunnels and history of contact with dog and cat feces

Diagnosis of Onchocerciasis

Demonstration of microfilariae in skin snips or blood Usually skin snips is taken from the infrascapular or gluteal region. Sample is obtained by raising the skin with a needle and shaving the epidermal layer with a razor. The specimen is incubated in saline for several hours and is then observed in dissecting microscope for the presence of non sheathed microfilariae

Diagnosis of Toxoplasma gondii

Demonstration of the organism as trophozoites/ cysts in tissues and body fluids: definitive method of diagnosis A. Trophozoite (Tachyzoite) stage: typically crescent shaped with a prominent, centrally placed nucleus B: Toxoplasma gondii cyst (Bradyzoites) in brain tissue stained with hematoxylin and eosin (100×). C: Zoom of Image B, T. gondii cyst Serology: Toxoplasma gondii Serologic profile (TSP): measure IgM, IgG, IgA and IgE To diagnose congenital toxoplasmosis Amniotic fluid (obtained by Amniocentesis): PCR- test of choice during prenatal (before birth) diagnosis Detection of IgM and IgA antibodies in new born

Streptogramins

Derivatives: Quinupristin, Dalfopristin Mechanism of Action: Both drugs given at the same time: synergistic action Inhibit protein synthesis: Dalfopristin - binds to 50s and prevent peptide chain elongation Quinupristin: causes premature release of peptide Pharmacology: bactericidal, Narrow spectrum: Gram positive Recommended for vancomycin resistant Staphylococcus and Enterococcus

Treatment for Bedbugs

Diagnosis: Detection of tiny spots of blood from dead insects on bedding Observation of pattern and location of bites Treatment: Calamine lotion to relieve itching Antihistaminics Prevention and control Proper hygiene Malathion or lindane to treat mattresses and beds

Diagnosis of Echinococcosis granulosus

Difficult; x-rays, CT scans, MRI, serology detect antigens, skin test (Casoni's reaction)-An immediate hypersensitivity reaction. Intradermal injection of 0.2 ml of a fresh sterile hydatid fluid produces within half an hr, in all positive cases, a large wheal (5 cm in diameter) with multiple pseudopodia. It fades in an hour. Hydatid fluid from human cases (removed by operation) or from animals is used as antigen.

Stoke's Method

Diffusion test Müeller-Hinton agar plate is inoculated by streaking the control strains evenly across the upper and lower thirds of the plate,and the test strains between the control ,leaving a distance of not more than 5mm on each side of the control strain. Measure the radius of the inhibition zone from the edge of the disc to the edge of the zone. Sensitive (S): Zone radius is wider than or equal to,or not more than 3mm smaller than the control. Intermediate (I): Zone Radius is > 2 mm but smaller than the control by > 3mm. Resistant (R): No zone of inhibition or zone radius measures 2mm or less

Kirby-Bauer method

Diffusion test Place paper disks impregnated with known conc. of antibiotics on a smear of culture on semisolid/solid media (eg, MHA: Mueller-Hinton agar), measure zone of inhibition in mm The size of the zone is compared with standard zone of inhibition to determine the sensitivity of the organism to that drug Report as: Resistant (R) -equal to or less than 14 mm Intermediate (R) -15-16 mm Sensitive (S)- equal to or more than 17mm Zone of inhibition measured in the test is compared with the standard given by CLSI guidelines Cheap, easy, but not quantitative

UV microscopy

Direct Fluorescent Antibody Staining (DFA) Detection and identification of viruses in patient's tissue/specimen or viral culture

Echinococcus granulosus

Dog tapeworm Epidemiology: worldwide; Definitive host: dog (commonly) Intermediate host: sheep, human (Human is an accidental host) Transmission: Fecal-oral: food, water, fingers contaminated with dog's feces Morphology: Eggs, larvae and Adult Adult-only three proglottids, in the intestine of dogs, Larvae in tissue of sheep/human: big fluid filled cyst (hydatid cyst)

Plasmodium Species Differentiation

Done on Thin Films P. falciparum: infects RBC of all ages P. vivax and P. ovale: young RBCs P. malariae: old RBcs P. falciparum demonstrates no selectivity in host erythrocytes and invades any red blood cell (RBC) at any stage in its existence. Also, multiple merozoites can infect a single erythrocyte. Thus three or even four small rings may be seen in an infected cell. P. falciparum is often seen in the host cell at the very edge or periphery of the cell membrane, appearing almost as if it were "stuck" on the outside of the cell. This is called the appliqué or accolé position and is distinctive for this species (Murrary)

Bacterial chromosome

Double stranded DNA Single chromosome, circular Haploid No introns No nuclear membrane Highly coiled into supercoils Two enzymes DNA gyrase (Topoisomerase II) Topoisomerase IV In haploid organisms a mutation on a gene has profound effect than in Eukaryotes. Role of DNA gyrase and Topoisomerase and action of Flouroquinolones: In Gram negative organism: DNA gyrase becomes the primary target for Flouroquinolones In Gram positive organism: Topoisomerase IV is the primary target, DNA gyrase remains as a secondary target

Bacterial DNA

Double-stranded molecule twisted into a helix (similar to a spiral staircase). The two strands are comprised of a sugar-phosphate backbone and attached bases. 4 nucleobases, sugar, phosphate Thymine - Adenine, 2 Hydrogen bonds Guanine - Cytosine 3 Hydrogen bonds Genetic code; same like eukaryotic cells The smallest bacteria - Mycoplasma - 0.58 x106 base pairs and carry 475 potential genes A typical bacteria, Escherichia coli, 4.639 x 106 base pairs and carry 4288 potential genes

Treatment of Leishmaniasis

Drug of choice for all forms-sodium stibogluconate (Antimonial/heavy metal) Alternatives For Visceral : Amphotericin B (liposome formulation), oral miltefosine, paromomycin, sitamaquine Cutaneous: Miltefosine plus fluconazole, Amphotericin B Muco-cutaneous: Amphotericin B Prevention and control Prompt treatment of cases Control of vector and reservoir host Use screening and insect repellents Vaccination under trial

Treatment of Filarial Elephantiasis

Drug of choice- Diethylcarbamazine (DEC) stimulates cholinergic receptors. Causes muscular paralysis, enhances adherence of leucocyte on parasite -targets larvae, No effective drugs for adult worms Supportive and surgical therapy may be needed Prevention and Control: Education, vector control, insect repellents and early treatment of infected cases

Treatment for Ascariasis

Drug of choice: Albendazole or Mebendazole Prevention: Education, Improved sanitation and avoidance of human feces as fertilizer

Treatment, Prevention and Control

Drug of choice: Tetracycline Prevention and control similar to amoebiasis When traveling to endemic tropical countries, Balantidium coli infection can be prevented by following good hygiene practices. All fruits and vegetables should be with clean water when preparing or eating them, even if they have a removable skin.

Treatment of Cystoisospora belli

Drug of choice: Trimethoprim-Sulfamethoxazole Prevention and Control: Maintaining personal hygiene and sanitary conditions

Treatment of Hymenolepis nana

Drug of choice: praziquantel ) has broad spectrum of activity-effective against various cestodes and Trematodes. It is a calcium agonist. Increase in calcium level results in tetanic muscular contractions and destruction of tegument. It acts synergistically with the host immune system. The drug causes disruption of the parasite surface and tegument, allowing antibodies to attack parasite antigens not normally exposed on the surface. Prevention and control: proper hygiene, treatment of cases

Life cycle of Schistosoma spp.

Eggs are excreted with feces or urine. Under optimal conditions the eggs hatch and release miracidia , which swim and penetrate specific snail intermediate hosts. The stages in the snail include 2 generations of sporocysts and the production of cercariae. Upon release from the snail, the infective cercariae swim, penetrate the skin of the human host , and shed their forked tail, becoming schistosomulae . The schistosomulae migrate through several tissues and stages to their residence in the veins . Adult worms in humans reside in the mesenteric venules in various locations, which at times seem to be specific for each species . For instance, S. japonicum is more frequently found in the superior mesenteric veins draining the small intestine , and S. mansoni occurs more often in the superior mesenteric veins draining the large intestine. However, both species can occupy either location, and they are capable of moving between sites, so it is not possible to state unequivocally that one species only occurs in one location. S. haematobium most often occurs in the venous plexus of bladder , but it can also be found in the rectal venules. The females (size 7 to 20 mm; males slightly smaller) deposit eggs in the small venules of the portal and perivesical systems. The eggs are moved progressively toward the lumen of the intestine (S. mansoni and S. japonicum) and of the bladder and ureters (S. haematobium), and are eliminated with feces or urine, respectively . Pathology of S. mansoni and S. japonicum schistosomiasis includes: Katayama fever, hepatic perisinusoidal egg granulomas, Symmers pipe stem periportal fibrosis, portal hypertension, and occasional embolic egg granulomas in brain or spinal cord. Pathology of S. haematobium schistosomiasis includes: hematuria, scarring, calcification, squamous cell carcinoma, and occasional embolic egg granulomas in brain or spinal cord.

Diagnosis of Schistosomiasis

Eggs in urine or stool or biopsy, Serology (ELISA) Schistosoma japonicum egg- contain a miracidium enclosed in a shell , have a lateral spine but is inconspicuous, smaller than that of S. mansoni (70-100 ×55-65 µm ) S. haematobioum egg- presence of terminal spine, S. mansoni- Prominent lateral spine, eggs are 115-175 ×45-70 µm

Hymenolepis nana- life cycle

Eggs of Hymenolepis nana are immediately infective when passed with the stool and cannot survive more than 10 days in the external environment . When eggs are directly ingested by humans (in contaminated food or water or from hands contaminated with feces), the oncospheres contained in the eggs are released. The oncospheres (hexacanth larvae) penetrate the intestinal villus and develop into cysticercoid larvae . Upon rupture of the villus, the cysticercoids return to the intestinal lumen, evaginate their scolices , attach to the intestinal mucosa and develop into adults that reside in the ileal portion of the small intestine producing gravid proglottids . Eggs are passed in the stool when released from proglottids through its genital atrium or when proglottids disintegrate in the small intestine. When eggs are ingested by an arthropod intermediate host (various species of beetles and fleas may serve as intermediate hosts), they develop into cysticercoids, which can infect humans or rodents upon ingestion and develop into adults in the small intestine. An alternate mode of infection consists of internal autoinfection, where the eggs release their hexacanth embryo, which penetrates the villus continuing the infective cycle without passage through the external environment . The life span of adult worms is 4 to 6 weeks, but internal autoinfection allows the infection to persist for years. H. nana is one of the exception to the general rule that the helminths do not multiply inside the body of the definitive host.

Morphology of Schistosoma spp.

Eggs, larvae (various stages) and adults Adults: The sexes are separate, the male and female live attached to each other. This ensures fertilization Males are shorter and stouter than females, lateral margins of males are folded to form gynaecophoric canal ('Schist') The female resides in the groove in the male [i.e, the gynecophoric canal ('Schist')] where he continuously fertilizes her eggs. There are 3 medically important species: can be distinguished by the appearance of their eggs in the microscope S. mansoni: have a prominent lateral spine S. japonicum: have a very small lateral spine S. haematobium: have a terminal spine Unlike other trematodes, Schistosoma eggs are bile stained but not operculated forked tailed cercariae are the infective form adults are not typical leaf like but more elongated have separate sexes

Disinfection

Elimination of disease producing (pathogenic) Micro-organism. Frequently toxic to apply to tissue but are commonly used on inanimate surfaces.

Clonorchis sinensis life cycle

Embryonated eggs are discharged in the biliary ducts and in the stool . Eggs are ingested by a suitable snail intermediate host ; there are more than 100 species of snails that can serve as intermediate hosts. Each egg releases a miracidia , which go through several developmental stages (sporocysts , rediae , and cercariae ). The cercariae are released from the snail and after a short period of free-swimming time in water, they come in contact and penetrate the flesh of freshwater fish, where they encyst as metacercariae. Infection of humans occurs by ingestion of undercooked, salted, pickled, or smoked freshwater fish . After ingestion, the metacercariae excyst in the duodenum and ascend the biliary tract through the ampulla of Vater. Maturation takes approximately 1 month. The adult flukes (measuring 10 to 25 mm by 3 to 5 mm) reside in small and medium sized biliary ducts. In addition to humans, carnivorous animals can serve as reservoir hosts.

Amoebiasis (amoebic dysentery)

Entamoeba histolytica Intestinal (large intestine) - IP: 4-5 days: dysentery (bloody diarrhea), abdominal pain, cramping; Severe case: numerous bloody stools/day Asymptomatic carriage Extra intestinal: liver abscess: seen approx. 5% of intestinal inf. pain and tenderness in right hypochondrium, fever, hepatomegaly (lower border of the liver palpable), transmission to other regions Spleen and cutaneous amoebiasis brain abscess Genital abscess - (in homosexual men)

Intestinal Nematodes

Enterobius vermicularis - Pin worm Ascaris lumbricodes - *S Giant worm (round worm) Ancylostoma duodenale/*S Necator americanus Hookworm Trichuris trichiura- Whip worms Strongyloides stercoralis* Threadworm Trichinella spiralis - * Pig worm *Have tissue stages as well *Soil transmitted helminths

Enveloped vs Naked Viruses

Enveloped Environmentally labile: Spread - must stay wet, large droplets, secretions, blood and organ transplant Enter cells by fusion with cytoplasmic membrane lipids Usually released by budding through the cell membrane with no cell death Cell to cell spread by syncytia may occur Naked Environmentally stable, Easily spread by water, dust, food, hand to hand, small droplets, fomites, etc. Naked viruses usually enter cells through receptor mediated avenue Naked viruses most often exit host cells by lysis and death of the cell

Herpes virus

Enveloped with Icosahedral capsid ds DNA, tegument between capsid and envelope-containing viral proteins and enzymes for replication

HIV

Enveloped with helical capsid Genome: Segmented RNA, Two identical positive ss RNA strands Surface glycoproteins - for adhesion and entry Packed enzymes: Reverse transcriptase, integrase , and proteases

Paramyxovirus

Enveloped with helical capsid Non Segmented, negative sense RNA genome, carry RNA dep. RNA polymerase F: mediates cell entry by inducing fusion between the viral envelope and the cell membrane HN/ H, G: attachment proteins, with Hemagglutinin and/or neuraminidase activity

Rabies virus

Enveloped with helical capsid bullet shaped, negative sense ss RNA Virus

Influenza virus

Enveloped with helical capsid Segmented, negative sense ssRNA genome Peplomers: 1. Hemagglutinins - binds and agglutinate RBC 2. Neuraminidase: an enzymes ; splits polymers of sialic (acetylneuraminic) acid to get released RNA dep. RNA polymerase

Mechanisms of Aminoglycosides Resistance

Enzymatic Modification of the drug: -Acetylation by acetyltransferases -Adenylation by adenyltransferases -Phosphorylation by phosphotransferases Transport Interference: decreased uptake Mutation of ribosomal binding Site Accelerated Export of Drug

Loa loa

Epidemiology: Equatorial rain forests of central and west Africa, infects human and other forest animals, such as monkeys Transmitted by mango fly (deer fly)-Chrysops spp

Babesia microti

Epidemiology: Found where Borrelia burgdorferi (Lyme disease) is found, North east US. Reservoir: Rodents; deer, cattle transmitted by tick (Ixodes dammini); or by blood transfusion Morphology: Sporozoan Exists in different forms - sexual and asexual reproduction. Pathogenesis: Infective form: Sporozoites (pyriform bodies) Infect and lyse RBC Clinical disease: Malaria like syndrome Incubation Period: 1-4 wks, General malaise, Fever without periodicity, headache, chills, sweating, fatigue, hemolytic anemia; hepatosplenomegaly in severe case

T. brucei (african sleeping sickness)

Epidemiology: Transmitted by Glossina (Tsetse fly) - T. b. gambiense: humans as the main host (vector prefers shaded stream banks proximity to human dwellings)-98% infection T. b. rhodesiense : human and cattle, and antelopes (Vector prefers brush land rather than stream banks)-2% infection Morphology: flagellate

Naegleria fowleri

Epidemiology: Ubiquitous in nature Reservoir: Warm water bodies such as heated swimming pools, hot tubs, hydrotherapy and medicinal pools, aquariums and sewage Transmission: Acquired during warm summer months from contaminated lakes - or in hot tubs, via the olfactory mucosa and nasal tissues Risk Factors/High Risk Populations: Mostly young children

Toxoplasma gondii

Epidemiology: World wide, two hosts - definitive host - cat family, intermediate host: man, cattle, rodents. Transmitted by: a) oral route: fecal (cat feces)-oral; or consumption of meat with cyst; b) blood transfusion or organ transplantation; and c) Transplacental route Morphology and life cycle: Sporozoan; 3 important forms: Oocyst, Tachyzoites and Bradyzoites; undergo sexual (Intestinal) and asexual (extra-intestinal) reproduction

Entamoeba histolytica

Epidemiology: world wide, highest incidence in tropical and subtropical regions; Transmission by fecal oral route; homosexual men; asymptomatic carriage common; prevalence in US: 1-2% Biology: Amoeba;trophozoite and cyst (maximum 4 nuclei)

Cryptosporidium parvum

Epidemiology: world wide, infects human and animals, millions of Crypto parasites shed in stools. Transmission by fecal- oral route, Approx. 748, 000 cases every year in US Biology: Sporozoan (coccidian) - exists in different forms, sexual and asexual reproduction. Acid fast oocyst (infective stage and diagnostic stage) Pathogenesis and Clinical disease: Adheres on the epithelial cells of the small intestine AIDS associated diarrhea, non bloody diarrhea, chronic, up to 50 stools Infects healthy persons as well.

E-test

Epsilometer test MIC determined from the test is compared with the standard given by CLSI guidelines A strip of paper with decreasing concentration of antibiotics Advantage : quantitative: measures Minimum Inhibitory Concentration (MIC)

Spontaneous mutation

Error during replication Mutation rate in viruses is high due to the poor fidelity of viral polymerases Mutation rate > in RNA than DNA virus because RNA viruses do not have error-checking mechanism Viruses are subject to the same type of mutations as other organisms Different types of mutations - resulting in variety of mutants Lethal mutant - due to inactivation of essential genes, can't replicate Defective mutant- deletion/mutation of gene/s: able to replicate with the help of other viruses Host range mutant - change of host/tissue specificity Attenuated mutant - causes less serious/no disease (vaccines) Conditional mutant: (eg temperature sensitivity of influenza live vaccine - can multiply at lower temp of URT but not LRT

Toxicity of oxygen

Especially harmful to obligate anaerobes Obligate anaerobes lack superoxide dismutase and catalase and/or peroxidase, and therefore undergo lethal oxidations by various oxygen radicals when they are exposed to O2 Superoxide dismutases are a class of enzymes that catalyze the conversion of superoxide into oxygen and hydrogen peroxide. Catalase convert hydrogen peroxide to oxygen and water. Tolerant anaerobes with low catalase and peroxidase levels are known

Alcohols

Ethanol and isopropanol Dissolve lipids (cell membranes) and denature proteins Bactericidal against many, but not against spores and non-enveloped virus More effective at 70% than 100%, because more effective in presence of water Commonly used to disinfect skin, and items such as thermometers

Formol Ether Concentration Technique

Ether adsorbs fecal debris & floats. Formalin fixes/ preserves the specimen.

Laboratory Diagnosis of Intestinal Amoebiasis

Examination of stool: -Macroscopic examination: offensive, darkbrown semi-fluid stool mixed with blood and mucous -Microscopic examination: Demonstration of E. histolytica-Cysts/trophozoites Presence of Cellular exudate and Charcol-Leyden crystals Charcot-Leyden crystals are slender and pointed at both ends. They consist of Lysophospholipase (an enzyme synthesized by eosinophils) and are produced from the breakdown of eosinophils PCR and DNA probe assay

Morphology of leishmania

Exist as flagellate (promastigote) and non flagellate form (amastigote form) Kinetoplast: a mass of mitochondrial DNA lying close to the nucleus

Antigenic Variation

Existing in multiple types Antigenic/phase variation: programmed gene rearrangement Switch genes on/off : NO MUTATION but results in phenotype switching Transcriptional regulation of alternative genes. Help the bacterium evade the host immune system.

Invasion or Spreading Factors

Exoenzymes : act on the extracellular matrix Tissue degrading enzymes Examples : Proteases, phospholipases hyaluronidase, collagenase, fibrinolysin (streptokinase) Induction of phagocytosis and spread without leaving the cell: Eg. Shigella and Listeria

Secretion systems

Exotoxins are released through special apparatus Some transport the toxins directly into the extracellular spaces Others inject the toxin directly to the target host cell via structures that serve as "molecular syringe " Eg of bacteria with Type III secretion system: Pseudomonas, Shigella, Salmonella, Yersina pestis Bacterial secretion system are named as Type I, II, III, IV, V and VI. Type I, II, V deliver the toxin to the extracellular space. Type III, IV, and VI are syringe like apparatus

Pathogenesis of lice

Feeds on blood Injects saliva into the skin that induces hypersensitivity reaction Intense itching, pruritic red papules Excoriation (act of abrading or wearing off the skin) and secondary bacterial infection can occur

Life cycle

For survival and reproduction, many parasites evolve through a number of morphologic stages and several environments or different hosts. The sequence of morphologic and environmental stages is referred to as the life cycle.

Immunological fungal diagnosis

For systemic mycosis Dermal hypersensitivity testing (like tuberculin test) Serology: Detection of antibody (4x increase of paired sera) Detection of fungal antigens in patient's sample

Focus Assay

For viruses with oncogenic potential

Superantigens

Form bridges between the MHC II (beta chain) of macrophages or other APCs and TCR of T cells Rate of T cell activation: 1/5 versus 1/10,000 to 100,000 (Superantigen Vs Other antigens) High levels of cytokines in circulation (cytokine storm) - Toxic shock syndrome - life threatening multi organ involvement. Examples: Toxic Shock Syndrome Toxins, TSST (Staphylococcus aureus) Streptococcal pyrogenic exotoxin (Spe) A and C (Streptococcus pyogenes) Toxic shock syndrome can affect most organ systems in the body, including the skin, lungs, liver, kidneys, blood, GI, and pancreas. Fever, rash, low pb etc

Acanthamoeba castellani Life Cycle

Found in soil; fresh, brackish, and sea water; sewage; swimming pools; contact lens equipment; medicinal pools; dental treatment units; dialysis machines; heating, ventilating, and air conditioning systems; mammalian cell cultures; vegetables; human nostrils and throats; and human and animal brain, skin, and lung tissues. Unlike N. fowleri, Acanthamoeba has only two stages: cysts and trophozoites , in its life cycle. No flagellated stage exists as part of the life cycle. The trophozoites replicate by mitosis. The trophozoites are the infective forms, although both cysts and trophozoites gain entry into the body through various means. Entry can occur through the eye , the nasal passages to the lower respiratory tract , or ulcerated or broken skin . When Acanthamoeba spp. enters the eye it can cause severe keratitis in otherwise healthy individuals, particularly contact lens users . When it enters the respiratory system or through the skin, it can invade the central nervous system by hematogenous dissemination causing granulomatous amebic encephalitis (GAE) or disseminated disease , or skin lesions in individuals with compromised immune systems. Both cysts and trophozoites of Acanthamoeba spp are found in tissue

Leishmania spp.

Four species L. donovani : causes kala-azar (visceral leishmaniasis) L. tropica L. mexicana L. braziliensis: mucocutaneous Leishmaniasis Epidemiology : World wide with restricted distribution. Favor arid, dry warm environment. Also infects animals (dogs and rodents). Transmitted by Sand fly, Phlebotomus spp. The second-largest parasitic killer in the world (after malaria) An estimated 1.3 million new cases and 20 000 to 30 000 deaths occur annually (WHO).

Giardia lamblia

G. duodenalis/G. intestinalis Epidemiology: world wide; In US, Giardia infection is the most common intestinal parasitic disease Also Infects other animals (beavers and muskrats) Transmission: fecal oral- mostly via contaminated water (such as streams, rivers); food and fingers; oral-anal sexual Risk factors-travel to known endemic areas, consumption of inadequately treated water, day care centers and oral-anal sexual practices Biology: flagellate - cyst and trophozoite Cyst: oval, 4 nuclei, axostyle/axoneme Trophozoite: Tennis/badminton racket appearance, two nuclei, 4 pairs of flagella, axoneme, sucking disc on ventral surface, 'Falling leaf' motility

Transformation

Gene transfer resulting from the uptake by a recipient cell of naked DNA from a donor cell. Certain bacteria (e.g. Bacillus, Haemophilus, Neisseria, Pneumococcus) can take up DNA from the environment and the DNA that is taken up can be incorporated into the recipient's chromosome. Successful gene transfer is dependent on the absence of restriction endonucleases Most important mechanism of genetic transfer in Gram positive microorganisms such as Streptococcus pneumoniae Cells must be competent Under the control of extracellular Competence Factor (CF) Uptaken DNA-Sensitive to endonucleases Occurs in nature and it can lead to increased virulence. In addition transformation is widely used in recombinant DNA technology.

Lice

General Properties: 2-4 mm long Two species: Pediculus humanus- elongated body: two subspecies: P.h.capitis (head louse) P.h.corporis (body louse) Pthirus pubis (pubic louse)short body Nits - eggs of lice- attached to hair shaft Lice do not have wings unlike other insects Epidemiology: Worldwide, Common in US Transmission: Head lice: By sharing of hair brushes/combs, hats and towels; common in children Body lice: By personal contact or by clothing Pubic lice: By sexual contact

Ticks

General Properties: Arachnids Female ticks require blood meal for maturation of their eggs Found in grassy woodland areas and attracted by CO2 and warmth from humans Comprise 2 large families Ixodidae (hard tick): hard dorsal plate or scutum, mouth parts visible from above Argasidae (soft tick): leathery body that lacks hard covering (scutum), mouth parts ventrally Epidemiology: Wooded and rural areas worldwide Ticks of medical importance in US: Hard ticks: Dermacentor variabilis (American dog tick)-More common in Eastern US D. andersoni (Rocky mountain wood tick)-More common in Western US Ixodes dammini (deer tick) Soft ticks: Ornithodorus spp. Risk factors: Exposure in wooded areas, staying in rural cabins inhabited by small rodents (which serve as host for ticks)

Taenia spp: life cycle

Humans are the only definitive hosts for Taenia saginata and Taenia solium. Eggs or gravid proglottids are passed with feces ; the eggs can survive for days to months in the environment. Cattle (with T. saginata) and pigs (with T. solium) become infected by ingesting vegetation contaminated with eggs or gravid proglottids . In the animal's intestine, the oncospheres hatch , invade the intestinal wall, and migrate to the striated muscles, where they develop into cysticerci. A cysticercus can survive for several years in the animal. Humans become infected: by ingesting raw or undercooked infected meat. In the human intestine, the cysticercus develops over 2 months into an adult tapeworm, which can survive for years. The adult tapeworms attach to the small intestine by their scolex and reside in the small intestine . Length of adult worms is usually 5 m or less for T. saginata (however it may reach up to 25 m) and 2 to 7 m for T. solium. The adults produce proglottids which mature, become gravid, detach from the tapeworm, and migrate to the anus or are passed in the stool (approximately 6 per day). T. saginata adults usually have 1,000 to 2,000 proglottids, while T. solium adults have an average of 1,000 proglottids. The eggs contained in the gravid proglottids are released after the proglottids are passed with the feces. T. saginata may produce up to 100,000 and T. solium may produce 50,000 eggs per proglottid respectively. by ingestion of contaminated water or eating undercooked vegetables containing eggs of T. solium (Humans don't get infected with T. saginata in this way!!!)

Hookworm: Life cycle

Humans get infected when an infective larvae, filariform, penetrate the skin. From the skin they enter the venules and are carried to the heart and lungs where they grow and eventually break out into the alveoli and pass up the respiratory tree. After they are swallowed, they attach to the intestinal mucosa and become sexually mature in 5 to 6 weeks. Females deposit eggs that are passed in the feces. In the proper soil, under ideal conditions, the eggs hatch in 1 to 2 days. Temperatures between 25°C and 35°C and a shady, sandy, or loamy soil with vegetation favor larval development. The rhabditiform larvae that emerge feed on bacteria and organic debris, moult twice, and develop into slender, infective filariform larvae in 5 to 8 days. The filariform larvae do not feed; if they are unable to penetrate a host, they die in a few weeks. Most adult worms usually live for 1-2 years but longer longevity is possible.

Laboratory Diagnosis of Viral Disease

I. Direct microscopic examination of clinical specimen Light/compound microscopy: Cytopathic effect (CPE). UV microscopy: Detection of viral antigens by fluorescent Ab staining Electron microscopy, immunoelectron microscopy II. Culture: cell culture (sometimes, inoculation of eggs or animals) Identification: Assessment of Cytopathic effect (CPE), Hemadsorption and other characters Detection of viral antigens by UV microscopy Quantification: viral titer-plaque assay Assessment of oncogenic potential (focus assay) III. Serological analysis: antibody detection/titer ELISA, Hemagglutination inhibition assay Neutralization tests: block cytopathic effects Western blot IV. Detection of viral antigens in sample: ELISA, rapid tests etc. V. Molecular analysis of genetic material PCR and In-situ hybridization: in clinical specimen or in culture specimen

Baltimore Classification

I: dsDNA viruses (e.g. Adenoviruses, Herpesviruses, Poxviruses) (Polyoma, papillomaviruses use host coded DNA polymerase whereas Adeno and Herpesviruses use viral coded DNA polymerases) II: ssDNA viruses (+ strand or "sense"/-ve strand or antisense ) DNA (e.g. Parvoviruses) III: dsRNA viruses (e.g. Reoviruses) IV: (+)ssRNA viruses (+ strand or sense) RNA (e.g. Picornaviruses, Togaviruses) V: (−)ssRNA viruses (− strand or antisense) RNA (e.g. Orthomyxoviruses (influenza virus), paramyxoviruses (measles, mumps, respiratory syncytial virus etc), Rhabdoviruses (rabies virus etc)] VI: ssRNA-RT viruses (+ strand or sense) RNA with DNA intermediate in life-cycle (e.g. Retroviruses) VII: dsDNA-RT viruses (e.g. Hepadnaviruses i.e Hepatitis B virus)

RNA Viruses

III: dsRNA: have positive and negative sense RNAs; negative sense RNA is used as a template for mRNA synthesis, Carries RNAdep-RNApoly (viral) to make the mRNA and also the genome; eg. Rota virus IV: ss +ve RNA: can directly act as mRNA, but during replication of their genome, forms a negative strand RNA (template) and then mRNA; code (viral) RNAdep-RNApoly [picornavirus (eg.rhinovirus), toga virus (chickengungya virus) etc. V: ss -ve RNA: must bring (carry) RNAdep-RNApoly (viral) to make mRNA (which also acts as a template for replication of their genome); orthomyxovirus (influenza virus), paramyxo virus (measles), rabies virus etc. VI: ss +ve RNA passing through a DNA intermediate: use their reverse Transcriptase to make ds DNA and host DNA dep-RNApoly to make mRNA (retrovirus- HIV)

Phenotypic mixing coat component

If two different viruses infect a cell, progeny viruses may contain coat components derived from both parents and so they will have coat properties of both parents. This is called phenotypic mixing. IT INVOLVES NO ALTERATION IN GENETIC MATERIAL, the progeny of such virions will be determined by which parental genome is packaged and not by the nature of the envelope.

Dark Field Microscope

Illumination comes from the sides, thus making the background appear dark, and the organism on the slide appear light(bright).

Immunological diagnosis

In Vitro: Serology; Antibody or Antigen. In Vivo: skin tests : eg. PPD test

Cerebral malaria

Most severe neurological complication of infection with Plasmodium falciparum malaria; Coma; Only young ring forms and occasionally gametocytes peripheral blood Mortality high, surviving patients sustain brain injury- long-term neuro-cognitive impairments.

Echinococcus granulosus life cycle

In the normal life cycle of Echinococcus species, adult tapeworms (3-6 mm long) inhabit the small intestine of carnivorous definitive hosts, such as dogs, coyotes, or wolves, and echinococcal cyst stages occur in herbivorous intermediate hosts, such as sheep, cattle, and goats. A number of other suitable intermediate hosts, such as camels, pigs, and horses, are involved in the life cycle in many parts of the world. Humans also serve as the intermediate host. In humans, it is the presence of the cyst that cause disease - A small cyst might contain hundreds of protoscolices; a large cyst might contain tens of thousands! This tremendous reproductive potential poses a problem in the intermediate host including humans. The disease is most commonly found in people involved in raising sheep, as a result of the sheep's role as an intermediate host of the parasite and the presence of working dogs that are allowed to eat the offal of infected sheep. Most commonly affected organs are liver followed by lung. Space occupying lesion, if a hydatid cyst breaks open, the protoscolex (larvae) enter the blood stream, may reach any organ: Each protoscolex could grow into a new hydatid cyst. They may also reach the brain - Unrelenting headache

Treatment of T. Brucei

Indicated for all persons diagnosed Pentamidine for first stage T. b. gambiense infection is widely available in US Other drugs (suramin, melarsoprol, eflornithine, and nifurtimox) to treat Afr. Tryp. are available in the U.S. only from the CDC Prevention and Control Wearing long-sleeved clothes Inspection of vehicles before entering Avoiding bushes. Use of insect repellent

Gray baby syndrome

Infants skin appears gray with vomiting and shock- due to toxic concentration of Chloramphenicol. This occurs due to reduced glucuronyl transferase (responsible for detoxification of chloramphenicol) activity in infants.

Toxoplasma gondii congenital infection

Infection during pregnancy may lead to abortion, still birth, blindness and congenital defects of the fetus: Ocular: Chorioretinitis- blurred vision, photophobia, and eye pain Neurologic: Intracerebral calcification, hydrocephaly/ microcephaly, convulsions, mental retardation Cardiac: Cardiomegaly Intracerebral calcification. If a woman is infected for the first time during pregnancy the parasite can cross the placenta and cause fetal disease. Both the probability and severity of the disease depend on when the infection takes place during pregnancy. Early: low transmission, but severe disease Late: high transmission, more benign symptoms. Hydrocephaly.

Diagnosis of Taenia solium

Intestinal-demonstration of eggs/proglottids in stool Cysticercosis: X-ray, CT, MRI imaging, Biopsy Eggs of Taenia Spherical and brown in colour (bile stained) Measure approx. 30-40 µm in diameter The inner embryophore is brown, thick walled and radially striated Contains an oncosphere with 3 pairs of hooklets Doesn't float in saturated solution of common salt

Treatment of Taenia solium

Intestinal: drug of choice-niclosamide Cysticercosis: drug of choice- praziquantel or albindazole Prevention and Control Proper cooking pork Washing kitchen utensils after cutting pork. Hygiene maintenance Health education regarding transmission

Pathogenesis of Plasmodium

Intracellular parasite, infects red blood cells and hepatocytes, dormancy in hepatocytes (except P. falciparum) P. falciparum: The processes of cytoadherence, rosetting, and agglutination are central to the pathogenesis of falciparum malaria Sequestration of RBCs containing mature forms of the parasite in vital organs (particularly the brain) interfere with microcirculatory flow and metabolism Clinical disease: Malaria : Incubation period: approx. 2 wks after bite. Fever, chills and sweating, shows periodic cycle. Febrile paroxysm synchronizes with erythrocytic schizogony, Types of fever: A. Tertian fever (with 48 hr cycle): recurs every 3rd d B. Quartan fever (with 72 hr cycle): recurs every 4th d C. Quotidian fever: recurs every 24 hrs Hepatosplenomegaly and anemia.

Pathogenesis of Toxoplasma gondii

Intracellular parasite: infect macrophages, muscle cells, epithelial cells - in different tissues Toxoplasmosis: affect many organs Clinical manifestations based on type of infection: I. Acquired infection: Immunocompetent Immunocompromised: severe II. Congenital infection:

Capsid Assembly

Is assembled around the viral genome. In addition, viral-coded envelope glycoproteins are inserted in the host cell's membranes by the Golgi apparatus. The viral envelope will be added later as the virus buds from the membrane (eg. Cytoplasmic) of the host cell during the release stage.

Generalized Transduction

Is transduction in which potentially any bacterial gene from the donor can be transferred to the recipient. Phages that mediate this process generally breakdown host DNA into smaller pieces and package their DNA into the phage particle by a "head-full" mechanism. Occasionally one of the pieces of host DNA is randomly packaged into a phage coat. Thus, any donor gene can be potentially transferred but only enough DNA which can fit into a phage head can be transferred. If a recipient cell is infected by a phage that contains donor DNA, donor DNA enters the recipient. In the recipient a generalized recombination event can occur which substitutes the donor DNA and recipient DNA .

Leishmania spp. Life Cycle

Is transmitted by the bite of infected female phlebotomine sandflies. The sandflies inject the infective stage (i.e., promastigotes) from their proboscis during blood meals . Promastigotes that reach the puncture wound are phagocytized by macrophages and other types of mononuclear phagocytic cells. Progmastigotes transform in these cells into the tissue stage of the parasite (i.e., amastigotes) , which multiply by simple division and proceed to infect other mononuclear phagocytic cells . Parasite, host, and other factors affect whether the infection becomes symptomatic and whether cutaneous or visceral leishmaniasis results. Sandflies become infected by ingesting infected cells during blood meals. In sandflies, amastigotes transform into promastigotes, develop in the midgut, and migrate to the proboscis

Treatment of Naegleria fowleri

Largely ineffective, early diagnosis critical Amphotericin B, New drug: Miltefosine Amphotericin B - considered investigational for this purpose Miltefosine is an experimental drug, which was initially developed for breast cancer but had shown some amoeba-killing capabilities in the lab. Amphotericin B is effective against N. fowleri in vitro, but the prognosis remains bleak for those who contract PAM, and survival remains less than 1% Therapeutic hypothermia: cooling the body below normal body temperature Only three known survivors Prevention: Avoid exposure to contaminated water: nose clip

Black widow spiders

Latrodectus mactans General characters Round shiny black abdomen Characteristic orange or reddish hourglass marking on the ventral surface Produce potent peripheral neurotoxin (Latrotoxin) Epidemiology: Worldwide-temperate and tropical regions, western and southern US, Old wooden building, cellars, hollow logs and outside toilet At Risk: Small children and Immunocompromised people

Oxazolidinones

Linezolid Mechanism of Action Binds to 50S and interfere with the formation of the initiation complex. Pharmacology: bacteriostatic, Gram positive, reserved for Vancomycin resistant Enterococcus faecium (VRE/VREF) Methicillin resistant Staphylococcus aureus (MRSA)/VRSA

Attenuation

Loss of/decreased virulence

Brown recluse spiders

Loxosceles spp. General characters: Relatively long legs Characteristic: a dark fiddle ( 'violin') shaped marking on the dorsal cephalothorax; 3 pairs of eyes in semicircle Venom is necrotoxin which also may have hemolytic properties Epidemiology: Worldwide; South, Central and Western US

Paragonimus westermani

Lung fluke Epidemiology: World wide, refugees from southeast Asia, Approx. 3 million people infected, Shore feeding animals (wild boars, pigs and monkeys) serve as reservoir Transmitted by eating raw or undercooked crabmeat Morphology: Adult Larva: various stages Eggs

Bacteriophage Life cycles

Lytic Cycle Virulent phage Leads to generalized transduction Lysogenic Cycle Temperate phage Leads to specialized transduction

Entamoeba histolytica Pathogenesis

Major virulence factors are Lectin/adherence protein Release of cytoxins and hydrolytic enzymes -Cytotoxin/Amoebapores (pore forming peptide): create pores in the target cell -Cysteine protease: (Thiol protease): degrades the extracellular matrix

Black water fever (dark urine)

Manifestation of falciparum malaria in previously infected subjects. Intra vascular hemolysis, fever, hemoglobinuria, Can result in acute renal failure and death In majority cases, parasites not detected in periph. blood.

Conidia

May arise directly from hyphae or from specialised stalk-like structures - conidiophore

Relapse of Malaria

May result from Recrudenscence: due to persistence of blood infection in which surviving population of erythrocytic forms are increased. Is a feature of P. falciparum infection Recurrence or true relapse: Persistence of exoerythrocytic forms in the liver in which erythrocytic schizogony commences again Is a feature of P. vivax, P. ovale and P. malariae infections

Bacterial Spores

Means of survival Formed in response to adverse conditions Occurs in unfavorable conditions such as starvation, desiccation, presence of disinfectants and in extreme temperature DNA replicates and separates, spore septum begins to form Double membrane encloses the DNA and cytoplasm Double membrane matures and becomes core wall Mother cell swells Spore coat develops Exosporium basal layer develops It contains- DNA, cell membrane, cytoplasm, cell wall, surrounded by a Spore Coat : contains high concentration of calcium bound to dipicolinic acid, plus a keratin-like protein Dehydrated : It contains about 70% less water than the mother cell. No detectable metabolic activity - makes them resistant to unfavorable conditions. Produced by some Gram positive & one Gram neg. Bacteria I. Gram positive bacilli: Obligatory aerobic: Genus Bacillus eg, B. anthracis, B. subtilis Obligatory anaerobic: Genus Clostridia eg. C. tetanus, C. welchii, C. botulinum Cocci: Gram positive cocci: Sporosarcina II. Gram Negative: Bacilli: Coxiella burnetii

Viral size and shape

Measured in nm Ranges from 18 nm to 300nm Assume different shapes

Immunological Methods

Measuring specific antibody levels against a particular pathogen - IgM - current infection IgG: paired sera- 4x increase OR : A single serum sample - determine titer and compare it with an upper limit of normal if it is established for that particular pathogen Detection of an antigen specific to a particular pathogen in a clinical (patient) sample in Vitro *Immunological techniques discussed in Immunological tools:

Pathogenesis of Fasciola hepatica

Mechanical irritations during migration of larva from the intestine to and through liver and its settlement in bile ducts, and Toxic secretions, hyperplasia of epithelium Clinical Disease In the acute phase (during migration of larva): nausea, vomiting, and abdominal pain/tenderness. Fever, rash, and difficulty breathing In the chronic phase (after the settlement of the parasite): inflammation and blockage of bile ducts, inflammation of the liver (hepatitis), gallbladder, and pancreas Halzoun is a painful pharyngitis caused by the presence of adult flukes on the posterior pharyngeal wall. The adult flukes are acquired by eating raw sheep liver.

Metronidazole

Mechanism of Action: Nitro group is reduced in vivo to form the active drug that disrupts DNA under anaerobic condition Pharmacology Initially as anti protozoan (Trichomonas) Bactericidal, narrow spectrum Effective against anaerobes, not aerobes Sensitivity testing for anaerobes is not performed routinely. Therefore, resistance is under-reported. The proposed mechanisms of resistance 1. Decreased drug uptake or increased efflux 2. Decreased drug activation/change in the biological target 3. Increased oxygen scavenging capabilities (SOD/catalase/ peroxidase) 4. Enhanced activity of DNA repair enzymes

Resistance in General

Mechanism of Resistance Intrinsic resistance Bacteria lacking peptidoglycan Seven major pathogens Chlamydia, Chlamydophila, Mycoplasma, Ureaplasma, Orientia, Ehrlichia and, Anaplasma Mutation of porin proteins - decrease permeability among some Gram negatives Inactivating enzymes: on plasmids Beta lactamase, some have extended spectrum (ESBL) activity gene carried on plasmid - could carry genes for other drug resistance - Multidrug R plasmids Alteration of Penicillin Binding Protein (form PBP 2A) Eg. Methicillin resistant Staphylococcus aureus (MRSA) (mec A gene mediated: alter target)

Conjugation

Mediated by the F factor, a plasmid that contain tra operons: (transfer region) where the genes coding for sex pili and other "fertility" factors are found Origin of transfer (OriT): where one of strands breaks and is transferred to the recipient Insertion sequence (For Hfr): a region that facilitate integration to the main chromosome Requires direct cell contact between 2 cells

Categorization of Gram Negative Rod

Medically relevant gram-negative bacilli include a multitude of species. Some of them cause primarily respiratory problems (Klebsiella pneumoniae, Legionella pneumophila, Pseudomonas aeruginosa), primarily urinary problems (Escherichia coli, Proteus mirabilis, Enterobacter cloacae, Serratia marcescens), and primarily gastrointestinal problems (Helicobacter pylori, Salmonella enteritidis, Salmonella typhi).

Categorization of Gram Negative Cocci

Medically relevant gram-negative cocci include the four types that cause a sexually transmitted disease (Neisseria gonorrhoeae), a meningitis (Neisseria meningitidis), and respiratory symptoms (Moraxella catarrhalis, Haemophilus influenzae).

Treatment for Entamoeba histolytica

Metronidazole followed by iodoquinol (quinoline derivative) Asymptomatic carriage: iodoquinol Prevention and Control Education Public and personal hygiene Use of boiled water/Protection of all food and drink from contamination by flies, cockroaches and rats Avoidance of raw vegetables and fruits Amoebicidal drugs: Tissue amoebicides (Trophozoites): Emetine, Dehydroemetine Luminal (Both trophozoites and cysts): Iodoquinol, Diloxanide Both Tissue and luminal: Metronidazole, Niridazole

Blood and tissue samples

Microscopic examination Blood, CSF, biopsy Serologic examination Antibody response Antigen detection Nucleic acid hybridization PCR Detection - In situ Culture Imaging; detect presence of parasites in tissues Xenodiagnosis Blood differential cell count = increased eosinophils in parasitic infection

Diagnosis of Malaria

Microscospy: Examination of thick & thin blood films Gold standard Demonstration of infected red blood cells; ring form, schizont and gametocyte form of parasite. Antigen detection by rapid diagnostic test (RDT): Aldolase enzyme (all Plasmodium) Lactate dehydrogenase (all Plasmodium & also specific to P. falciparum) Histidine rich protein-2 (specific to P. falciparum) Molecular: PCR based test

Trypanosoma cruzi in non-endemic countries

Migration routes from Latin America and estimation of the total number of infected individuals in non-endemic countries.

Treatment of Babesia microti

Mild to moderate case: Atovaquine + Azithromycin Severe: Clindamycin+ quinine/Exchange transfusion Prevention and Control Use of protective clothing and insect repellants Prompt removal of ticks, minimize exposure time The Ixodes nymphs that typically spread B. microti are so small (about the size of a poppy seed) that they are easily overlooked. But they usually must stay attached to a person for more than 36-48 hours to be able to transmit the parasite.

Determinants of Bacterial Pathogenesis

Mode of Transmission Adherence factors Ability to invade, spread and cause inflammation Toxin production: Products that kill or alter physiology of host cells Surviving host defenses Immunopathogenesis: Collateral damage due to host immune response or immune complication

Chemical Agents

Mode of action: disrupt cell membrane, denature proteins, break DNA. The rate of killing by a chemical depends on: Concentration of the chemical: Effectiveness usually is directly related to concentration. But not always E.g Alcohol - 70% is more effective than 95% Time of exposure Physiological condition of the microbe (eg. Vegetative Vs. spore) Presence of organic matter - affects exposure Population size - the number of bacterial cells Disruption of cell membranes: Alcohol, Detergents, Phenols (Acronym-ADP) Modification of proteins: 3H-Halogens (chlorine, Iodine), Heavy metals, Hydrogen peroxide; Alcohol, Aldehydes (Formaldehyde and Gluteraldehyde), Ethylene oxide Modification of nucleic acids: Aldehyde (formaldehyde and Gluteraldehyde), Ethylene oxide and Dyes (Crystal Violet, Malachite green)

Camouflage

Molecular mimicry: antigenic similarity with host Hiding within cells - intracellular growth

CPE (Cytopathic Effect) on cell culture

Morphological changes of human corneal epithelial cells infected with a virus. A: Normal human corneal epithelial cells exhibited a cobblestone appearance. B: After cells were infected with HSV-1, the cytopathic effect could be seen at 8 h p.i. The space between infected cells increased for 12 h (C) and 24 h (D), the cobblestone appearance disappeared and many giant multinucleated cells could be seen. Magnification: 200X.

A-B Toxins

Most bacterial toxins fall into this class Two units: A and B B unit binds to host cell receptor Determines the host cell specificity of the toxin After entering the cell the A unit cleaves or modifies a target molecule within the cell. The A unit is translocated through host plasma membrane after B binds (directly or through endocytosis).

Fungal Growth

Most fungi are aerobic, some may be facultative anaerobic Are heterotrophic - require organic matter for growth Most grow best at room temperature 20 -40 0C Fungi will grow well on slightly acidic media, slightly drier, higher osmotic pressure where bacteria do not Common culture media - Sabouraud dextrose agar (SDA) Selective for fungi: pH 5.6, osmotic pressure: Does not support bacteria Cycloheximide may be added to SDA to suppress fast growing non pathogenic fungi -To favor growth of pathogenic one in a mixture of same. Thermal dimorphism : Yeast at 37 0C and mycelial form at room temp (25 0C) Fungi can withstand higher osmotic pressures than most bacteria

Treatment of Toxoplasma gondii

Most infections in immunocompetent: resolve spontaneously Disseminated infection: Pyrimethamine plus sulfadiazine, Alternative: clindamycin plus pyrimethamine Cerebral edema and ocular infection: corticosteroid added Prevention and control Routine serologic screening for patients before organ transplantation and early in HIV infection (For sero+, Trimethoprim-sulphamethoxazole) Screening of Pregnant women (a part of 'TORCH' screening) Pregnant women and immunocompromised: avoiding raw or undercooked food, avoiding exposure to cat feces

Types of Staining Methods

Negative staining: Stain the background, not the object of interest: which will be transparent against colored back ground Eg. Capsule staining (India ink) Simple staining - one dye is used; reveals shape, size, and arrangement Differential staining - use a primary stain and a counterstain to distinguish cell types or parts (examples: Gram stain, acid-fast stain and endospore stain)

Side effects of aminoglycosides

Nephrotoxic 8th cranial nerve damage Hearing loss and/or loss of balance drug level monitoring required These drugs are ineffective in abscess. Do not penetrate cell wall of Gram positives. They are generally given with cell wall inhibitors to treat an infection with them.

Ectoparasite Neuromuscular manifestation

Neurotoxin mediated Ascending flaccid paralysis: Ticks Systemic arachnidism (Muscle spasm): Black widow spiders

Viral Genetics

New viral strains with properties different from the parent/wild type can arise by Spontaneous mutation Mutants can be point mutants (one base replaced by another) or insertion/deletion mutants. Recombination enables a virus to pick up genetic information from viruses of the same type and occasionally from unrelated viruses or even the host genome and/or Interaction between two genetically different viruses that infect the same cell Recombination Phenotypic mixing Complementation

Treatment of Chagas Disease

Nifurtimox and benznidazole (FDA not approved) In the U.S., drugs available only through CDC Prevention and Control Improved housing and spraying insecticide inside housing to eliminate triatomine bugs Screening for Chagas disease during blood donations Early detection and treatment of new cases

Hypersensitivity Mycotic Diseases

Non Infectious Airborne spores, hyphal fragments; Id reaction

Oxygen and Bacterial Growth

Obligate aerobes: require oxygen. Grow best at atmospheric concentration of oxygen. Microaerophiles: require oxygen at a lower concentration than the atmospheric conc. Facultative anaerobes: can grow in the presence or absence of oxygen. Aerotolerant anaerobes: They do not use oxygen but can grow in the presence of oxygen. Obligate anaerobes: Get inhibited by oxygen Examples: Obligate aerobes: Pseudomonas, Bacillus Micro-aerophiles: Helicobacter, Campylobacter Facultative anaerobe: Escherichia coli, Vibrio cholerae (They are generally aerobes but can grow in the anaerobically environment) Aerotolerant Anaerobes: Lactobacilli, Clostridium carnis, C. histolyticum, C. tertium etc. Obligate anaerobes: Clostridium tetani, Bacteroides.

Replicating virus

Often produce histological changes in infected cells. These changes may be characteristic or non-specific. Viral inclusion bodies are basically collections of replicating virus particles either in the nucleus or cytoplasm. Examples of inclusion bodies include the negri bodies and cytomegalic inclusion bodies found in rabies and CMV infections respectively. Although not sensitive or specific, histology nevertheless serves as a useful adjunct in the diagnosis of certain viral infection.

Katayama fever

Onset of oviposition results in a symptom complex featured by fever, chills, cough, urticaria, arthralgia, splenomegaly and abdominal pain

Host

Organism harboring a parasite. Definitive host: Animal harboring the adult or sexually mature stage of the parasite. Intermediate host: Animal in which development occurs but in which adulthood is not reached.

Diagnosis and treatment of scabies

Potassium hydroxide (KOH) -preparation of skin scraping or skin biopsy -demonstrates mite or their eggs or fecal pellets Treatment: Permethrin (Elimite)Apply from head to toe, leave on for 8-14 hr, rinse; may reapply in 7 days if live mites reappear Single application usually curative -drug of choice, Alternative-1% gamma benzene hexachloride (Lindane) Prevention and control Treatment of close contacts of the patient Treating or discarding fomites

Moist heat

Pasteurization: aim is to kill pathogenic bacteria in milk and some canned foods. 62 oC for 30 min followed by rapid cooling, or 72 oC for 15 seconds followed by rapid cooling 1350 C (275 0F) for 1 to 2 seconds- kills bacteria and most spores Boiling: at atmospheric pressure, 100 oC at sea level, can kill vegetative cells in 10 min. , but not spores. Not a means of sterilization. Tyndallization : intermittent boiling (three days in succession), can attain sterility, including spores. May be used for solutions that contain heat sensitive substance Exposure of 1000 C for 20 min on 3 successive days. Autoclaving: steam under pressure, 121 oC at 15 lb/sq inch for 15-20 min kills all microorganism including spores, but not prions 121 oC for 1 hr to destroy prions Sterilization control: Spores of Bacillus stearothermophilus

Coordinated expression of several genes

Pathogenicity Islands : Assemblage of several virulence genes in one or more contiguous DNA sequences Usually a transposon inserted into the chromosome or a plasmid Can be transferred as a unit and could be turned on by single stimulus Eg. Salmonella - 25 genes can be turned on by a change in pH in a phagocytic vesicle within macrophages

Heat

Physical Agent Denature proteins Dry heat: Incineration - sterilization by combustion Direct flaming : used to sterilize heat resistant materials for immediate use. Eg. Inoculating loop Dry hot air (Hot air oven): 160 oC for 1hr, used to sterilize heat resistant materials like glass ware Infrared combustion technology

Taenia solium

Pig Tapeworm Epidemiology: worldwide, intermediate host- pigs, humans- definitive (sometimes, intermediate host) Transmission: Eating undercooked pork 'measly pork' (containing larvae) Fecal-oral (from infected persons)- by ingestion of contaminated water or eating undercooked vegetables infected with eggs. Morphology: Eggs, Larvae (Cysticerci), Adults

Trichinella spiralis

Pigworm Adult worms: female 2.2 mm in length, males 1.2 mm Epidemiology: Worldwide, infects a wide variety of animals- carnivores/ omnivores PIGS main source for humans. Estimated 10,000 cases of trichinellosis occur every year worldwide; Temperate, Tropical and Polar regions Transmission: consumption of undercooked pork or wild carnivores such as BEAR, SEAL, that contain the larvae embedded in muscle tissue.

Antifungal Drugs

Polyenes : Amphotericin B, Nystatin Affects integrity of plasma membrane: Inserts in fungal membrane next to ergosterol; causes pore formation, ion leakage Azoles : Eg. Ketoconazole, Fluconazole inhibit plasma membrane synthesis: by interfering with ergosterol synthesis Echinocandins : eg. Caspofungin inhibits cell wall synthesis - interfere with glucan synthesis Nikkomycins: Inhibit cell wall synthesis: interfere with chitin synthesis Flucytosine : Inhibits nucleic acid synthesis Griseofulvin: : Inhibits cell division: interfere with microtubules (disruption)

Colistin

Polymyxin B, and Polymyxin E Structure: Basic polypeptide Mechanism of Action Cationic detergent Disrupts cell membrane Pharmacology: Bactericidal, narrow spectrum Gram negative bacilli (not for Gram positives) Side effects include neurotoxicity and acute renal tubular necrosis

Biotyping

Presence or absence of biochemical markers The formation of distinct biochemical end-products eg. carbohydrates fermentation Presence of certain bacterial enzymes and or toxins eg. Catalase, oxidase, hemolysins Use of specific nutrients - eg. E.coli using acetate as sole source of carbon Information from selective, differential media and enrichment media E.g Lactose fermentation and other colony characteristics

Application of Cell Culture

Presumptive identification of virus: by study of Cytopathic effect, Hemadsorption (Infected cell with hemagglutinin expressed on its surface + RBCs= Adsorption of RBCs on the surface of infected cell) Hemagglutination (Virus with hemagglutinin +RBCs= Agglutination) Interference (with the formation of CPE) and Decrease in acid production by infected cells Definitive identification of virus (grown in culture): by Neutralization*, Hemagglutination inhibition*, (*will be discussed under serology-slide no. 23) Immunofluorescence, Complement fixation, ELISA Others: Plaque assay: quantification of viral particles, titration Focus assay: determine oncogenic potential

Prion

Proteinaceous infectious agent Composition: only protein - no DNA or RNA Encoded by host cell genes Forms from post translational modification of gene products Normal protein (PrPc ) - has alpha-helical form Abnormal protein (PrPsc )- has beta-pleated sheet Extremely resistant to usual sterilization techniques Cause slow fatal neurodegenerative diseases in human and animals transmissible spongiform encephalopathies - Eg Creutzfeldt-Jacob disease (CJD)

Capsid

Proteins made up of repeated subunits known as capsomeres covers and protects the nucleic acid may have special host cell attachment properties arrangement of capsomeres determine the shape of the virus Icosahedral or helical

Replication

Protozoans: multiply inside the human body Intracellular or extracellular - depending on organism Helminths: most do not replicate inside the human body

Bacterial Cell Walls

Provides shape and helps cell to maintain its integrity under changing environmental conditions Importance from the medical point of view carries virulence factors It is a site of action for many antibiotics It is a site of action for body defense chemicals, such as lysozyme It is important in bacterial classification Gram positive, Gram negative, acid fast Made up of a polymer - Peptidoglycan (Murein) composed of multiple units of -N-acetylmuramic acid (NAM), with tetra-peptide chain (4 amino acids) coming off of the NAM. -N-acetylglucosamine (NAG) along with few other constituents

Nitrocef test

Rapid test for beta lactamase production are intended for the rapid testing of isolated colonies of Neisseria gonorrhoeae, Moraxella (Branhamella) catarrhalis, Staphylococcus spp., Haemophilus influenzae, Enterococcus spp., and anaerobic bacteria of the genera Bacteroides, Clostridium, Porphyromonas, Fusobacterium, and Prevotella. Disks are impregnated with nitrocefin (a chromogenic cephalosporin). As the amide bond in a beta-lactam ring is hydrolyzed by a beta-lactamase, nitrocefin changes color from yellow to red. Bacteria which produce beta-lactamase in significant amounts produce this yellow to red color change

Pathogenesis of Naegleria fowleri

Rare but fatal. Primary Amebic Meningoencephalitis (PAM). It starts with flu like symptoms, severe headache followed by Meningeal signs: high fever, stiff neck, vomiting; Olfactory hallucinations, focal neurologic deficits, and progresses rapidly (<10 days); and Coma and death.

Onchocerca volvulus

River blindness Epidemiology: Africa; and Central & South America (Guatemala, Mexico, Colombia and Venezuela) Transmitted by black fly - Simulium damnosum, breeds along fast flowing water - rivers and springs Adults live in subcutaneous tissue, forming nodules. Larvae concentrate in dermis (easily picked up by black flies)

Nematodes

Round worms Elongated, cylindrical, non-segmented worms, tapered on both ends Have complete digestive system The body is covered with a non cellular, highly resistant coating called cuticle. Separate anatomical sexes Female produces either eggs or larvae These eggs and larvae may be infective immediately or may require a period of development to reach the infective stage, influenced by weather and soil type Most common Nematode infection in US: Enterobiasis (pinworm infection)

Interferon Response

Secreted by infected cells bind to common interferon receptor on infected as well as non infected cells. The interferon receptor is linked to cytoplasm signalling molecules [Janus family of tyrosine kinases/Janus Kinase (JAK)] and which in turn is linked to STAT (Signal Transducer and Activator of Transcription). Activated STAT enters the nucleus and turns on several genes, including those proteins that help to inhibit viral replication. These include: -Oligoadenylate synthetase, activates an endoribonuclease (Rnase L) that degrades viral RNA. -The second gene activated by interferon is a serine-threonine kinase called PRK kinase - inactivates eIF-2 (an initiation factor) by phosphorylation, thus prevents protein synthesis, inhibits viral replication. -Another interferon induced protein called Mx protein, blocks viral transcription.

Amendments to Koch's postulates

Serological: antibodies or antigens specific to the pathogen in question should be detected Molecular: nucleic acid specific to the pathogen in question should be detected

Diagnosis of Toxocariasis and Baylisarcaris

Serology (ELISA), demonstration of the larvae in the affected tissue Diagnosis of VLM, NLM and OLM is based on the clinical findings, the presence of eiosinophilia, known exposure to dogs, cats or raccoons, and serological confirmation/detection of larvae in the affected tissue.

Myiasis

Specific myiasis: by flies which require a host for larval development eg. Human botfly: Dermatobia hominis Semi-specific myiasis: is caused by species which (i) usually deposit their eggs or larvae in decaying flesh or vegetable matter and at times deposit them on morbid tissue and (ii) are facultative parasites eg. Green bottle fly (Phaenicia spp.) Pathogenesis: Larvae in tissues induces an inflammatory response Clinical disease: Cutaneous myiasis-the most common one Others-nasal, oral, ocular, intestinal, genitourinary and cerebral forms (head trauma) The lesion is painful, erythematous papule Larva visible within a central pore Sense of movement

Cephalosporins

Structure: 7-Aminocephalosporanic Acid Betalactam ring + Dihydrothiazine Ring (6 membered) R group: Change in R group - 1st, 2nd, 3rd, 4th, 5th generations Mode of action and uses: same as penicillins Ist generation: Cephalexin, Cefazolin, narrow spectrum: Gram +ve 2nd generation: Cefuroxime, cefoxitin: expanded spectrum to a few Gram negatives 3rd generation: Ceftriaxone, ceftazidime : broader spectrum, more Gram negative bacteria 4th generation: Cefepime, Cefpirome: extended spectrum, against Gram negative including Pseudomonas aeruginosa, also against Gram +ve 5th generation: ceftobibrole (powerful antipseudomonal activity), ceftaroline

Aminoglycosides

Structure: Amino-sugars linked by glycosidic bonds to other sugar derivatives Various derivatives Streptomycin, Amikacin, Gentamicin, Tobramycin Neomycin, Kanamycin, Netilmicin Mechanism of Action Inhibit protein synthesis by interfering with the function of the 30S ribosome Inhibit initiation complex and cause misreading of mRNA Oxygen dependent uptake Pharmacology Bactericidal (binds irreversibly)- narrow spectrum Effective against aerobes- Gram negatives Streptomycin - Mycobacterium Poorly absorbed in GI Penetrate poorly in abscess (Penetration requires O2)

Macrolides

Structure: Large (13-16 Carbon) lactone ring and two sugars one or more deoxy sugars, usually cladinose and desosamine Derivatives: Erythromycin, Azithromycin, Clarithromycin Mechanism of Action Exert their effect by their reversible binding to the 23S rRNA of the 50S ribosomal unit. Binding to 50s ribosome Prevents the release of tRNA after formation of peptide bond Pharmacology: Bacteriostatic: Broad spectrum, Gram positive and negative, Chlamydia, and Mycoplasma Drug of choice for penicillin allergic patients Mechanisms of Resistance Alteration of 50S ribosomal subunit Enzymatic modification Side effects: GIT disturbances due to suppression of the normal flora

Vancomycin

Structure: Large glycopeptide Mechanism of Action: Inhibits cross linking of peptidoglycan by binding to terminal D alanines Pharmacology: Bactericidal, Narrow spectrum; effective against Gram positives ADR: Red man syndrome: Histamine released from mast cell/basophils Resistance: Van A and Van B genes replace last D alanine with a lactic acid - Gene carried on plasmids and transposon (multi-drug R) Resistant strains of Enterococcus spp (known as VRE) and Staphylococcus aureus problematic (known as VRSA) world wide VRE-Vancomycin resistant enterococci VRSA-Vancomycin resistant Staphylococcus aureus

Pathogenesis of Black widow bite

Systemic arachnidism (Neurotoxic disease): by latrotoxin Shortly after bite-sharp pain, followed by local redness, swelling and burning Systemic signs and symptoms also within an hour- Latrotoxin stimulates release of acetylcholine (pre-synaptically) Severe pain and spasm in the extremities, chest pain, nausea, vomiting, intestinal spasms and visual difficulties Abdominal tetanic cramps produce a firm or 'boardlike abdomen'-highly characteristic Acute symptoms usually subside within 48 hours Severe case-Paralysis, coma, cardiac or respiratory failure Diagnosis: Clinical as well as identification of typical spiders

Formation of asexual spores (Anamorph)

The shape, color and arrangement of asexual spores/spore forming structures are used in the identification of fungi Two basic forms: a. Conidia-naked spores, no sac, most common form ; different forms Eg, Chlamydoconidia, Microconidia, Macroconidia etc. b. Sporangiospores - contained in a sac like structure

Aseptic

The absence of microorganisms in tissue

Hyphae

The branching, threadlike tubes that make up the bodies of multicellular fungi

Acid Fast Cell Walls

The cell envelopes of these organisms are considerably more complex than other bacteria. Mycolic acid (long, branch chained fatty acids) covalently bound via a polysaccharide to peptidoglycan. Other mycolic acid-containing compounds and other complex lipids form a thick waxy membranous layer outside the peptidoglycan layer. Components: Peptidoglycan Lipid based polymers woven through out, e.g, Mycolic acid Trehalose dimycolate Lipoarabinomannan Arabinogalactan Cell wall resists intracellular killing Examples Mycobacteria, Nocardia

Enveloped viruses

The envelope is derived from the host cell membrane or nuclear membrane depending on the site of replication (cytoplasm or nucleus). The proteins on the envelope are viral proteins (rarely are host cell proteins found on the envelope). Enveloped with icosahedral capsid e.g. herpes virus, yellow fever virus, rubella virus Enveloped with helical capsid e.g. rabies virus, influenza virus, parainfluenza virus, mumps virus, measles virus

Gene flow in bacteria

The genetic information is stored as a continuous segment of DNA, and the messenger RNA can immediately direct the synthesis of the corresponding protein. In higher organisms, the gene is usually split, and the messenger RNA has to be processed by splicing before it can be translated into a protein. Unlike prokaryotes, most genes in higher eukaryotic cells contain large amounts - as much as 98% in the human genome regions called introns that are not part of the code for the final protein. These are interspersed among the coding regions or exons that actually code for the final protein.

Transcapsidation

The situation where a coat is entirely that of another virus, e.g. a retrovirus nucleocapsid in a rhabdovirus envelope. This kind of phenotypic mixing is sometimes referred to as pseudotype (pseudovirion) formation/Transcapsidation. The pseudotype described above will show the adsorption-penetration-surface antigenicity characteristics of the rhabdovirus and will then, upon infection, behave as a retrovirus and produce progeny retroviruses. This results in pseudotypes having an altered host range/tissue tropism on a temporary basis.

Viropexis

The process by which different classes of viruses, particularly picornaviruses and papovaviruses, enter the host cell in which they will be able to replicate. The hydrophobic structures of the capsid proteins may be exposed after viral binding to the cell (see VAP, viral attachment protein). These structures help the virion or the viral genome slip through the membrane.

Trichuris trichiura (Whipworm): life cycle

The unembryonated eggs are passed with the stool. In the soil, under moist and warm condition the eggs develop into a 2-cell stage, an advanced cleavage stage and then they embryonate; eggs become infective in 15 to 30 days. After ingestion (soil-contaminated hands or food), the eggs hatch in the small intestine, and release larvae The larvae moves to the colon, establish itself and mature to adult form. The adult worms are fixed with the anterior portions threaded into the mucosa. The females begin lay eggs 60 to 70 days after infection. Each female worm shed between 3,000 and 20,000 eggs per day. The life span of the adults is about 1 year.

DNA Viruses

There are 7 families Genome/DNA structure varies Double stranded linear (eg, herpes virus) Double stranded circular (complete) [eg, human papilloma virus] Partially double stranded circular - only in hepadnaviruses Single stranded linear - only in parvoviruses All replicate in the host cell nucleus except for poxviruses All have a neoplastic potential since they have an intra- nuclear residence and might damage host DNA They may also cause latent infection

Salmonella

Use phase variation to switch between different types of the protein flagellin. As a result, flagella with different structures are assembled. Once an adaptive response has been mounted against one type of flagellin, or if a previous encounter has left the adaptive immune system ready to deal with one type of flagellin, switching types renders previously high affinity antibodies, TCRs and BCRs ineffective against the flagella.

Light Microscopy of viruses

Used to monitor the cytopathic effect. Morphological change: Change in shape, such as the rounding of cells, aggregation, degeneration Loss of attachment to culture dish, loss of contact inhibition Syncytia formation (multinucleated cells) Inclusion bodies: aggregation of viral proteins or particles in the cytoplasm or nucleus, margination of chromatin Haemadsorption - cells acquire the ability to stick to mammalian red blood cells by expressing viral hemagglutinin antigens on their surface

Bright field Microscope

Uses the visible light source under the stage to produce a clear image. The Diaphragm adjusts the amount of light entering the stage. It consists of three objectives- the scanning power(usually 4x-6x), the low power(10-12x), and high power(40x). Maximum useful magnification: 1000-2000X eg, Compound Microscope

Trichomonas vaginalis

Very common agent of STDs Epidemiology: world wide, prevalence in developed countries-5-20% women and 2-10% men; In US: 3.7 million people infected, Transmission: sexual transmission sharing shower materials, through mother's infected birth canal- infection of infants Biology: flagellate; Anerobic exists as trophozoite only (no cysts!!!) one nucleus, four flagella and undulating membrane, a locomotory organelle of certain flagellate (trypanosome and trichomonad) parasites, consisting of a finlike extension of the limiting membrane with the flagellar sheath; wavelike rippling of the undulating membrane produces a characteristic movement. Costa: Ribbon like supporting structure at the base of undulating membrane

Fungal Colony Morphology

Yeast colony: opaque, compact, mucoid/dry, bacteria like, alcoholic odor, grow well at room temp in 24 hrs Molds colony : Hairy, cottony, velvety texture, may be colored (dematiaceous-due to pigment production). Vegetative hyphae: extend into growth medium, absorb nutrition Aerial (reproductive) hyphae: extend from the agar surface and often have spores- useful in identifying the mold

A-B Toxins Mode of Action

a. ADP-ribosylation of Elongation factor-2 G-protein - increase in cAMP Intracellular signalling cAMP and G protein: G proteins (guanine nucleotide-binding proteins) are a family of proteins involved in transmitting chemical signals outside the cell, and causing changes inside the cell b. Cleavage of rRNA The ADP-ribosyl group is removed from the coenzyme NAD (see dashed line) and is covalently attached to a host cell target protein. This causes the inactivation/hyperactivation of that target protein. c. Interference with release of neurotransmitters (Neurotoxin)

Anaerobic Culture

a. Gas Pak system b. Anaerobic chamber c. Reducing medium - Thioglycollate broth

Detection of Plasmodium antigens

pLDH (parasite lactate dehydrogenase) Rapid diagnostic test (RDT) is based on rapid immunochromtatographic lateral flow principle. Dye-labeled antibody, specific for target antigen, is present on the lower end of nitrocellulose strip or in a plastic well provided with the strip. Antibody, also specific for the target antigen, is bound to the strip in a thin (test) line, and either antibody specific for the labeled antibody, or antigen, is bound at the control line. Blood and buffer, which have been placed on strip or in the well, are mixed with labeled antibody and are drawn up strip across the lines of bound antibody. If antigen is present, some labeled antibody will be trapped on the test line. Excess-labeled antibody is trapped on the control line. The accumulation of microscopic dye particles on the thin band produces a visible line if sufficient antigen-labeled antibody complex is present.