PLE MICRO
malaria infective stage to MOSQUITOS, mature into TROPHOZOITES, ***both MALE AND FEMALE gametocytes have to be ingested for mosquito to become infectious
GAMETOCYTES
The standard autoclave conditions - To be effective, the autoclave must reach and maintain a temperature of __________ for _around _______________ by using saturated steam under at least _____ of pressure.
121° C 15-20 minutes 15 psi for prion control, the autoclaving time is extended to 1 hour!
The physician requests for mineral oil prep of the skin scrapings. What is the most likely microsopic finding? A. Mites B. Amastigotes and lymphocytes C. Lice D. Hyphae with conidia
A. Mites The diagnosis of scabies is usually made based upon the customary appearance and distribution of the rash and the presence of burrows. Whenever possible, the diagnosis of scabies should be confirmed by identifying the mite or mite eggs or fecal matter (scybala). This can be done by carefully removing the mite from the end of its burrow using the tip of a needle or by obtaining a skin scraping to examine under a microscope for mites, eggs, or mite fecal matter (scybala). However, a person can still be infested even if mites, eggs, or fecal matter cannot be found; fewer then 10-15 mites may be present on an infested person who is otherwise healthy.
When an exotoxin binds to a receptor, it activate T-cells by binding SIMULTANEOUSLY to a T-cell receptor and MHC II molecule on an antigen-presenting cell WITHOUT requiring an antigen. It activates large number of T cells to cause a cytokine storm. What is the nature of this exotoxin? A. Superantigen B. Protein synthesis inhibitor C. ADP-ribosylator D. Protease
A. Superantigen
OBLIGATE ANAEROBES
ABC of Anaerobes Actinomyces Bacteroides Clostridium
DOC for Severe or uncomplicated infections with P. falciparum
Artesunate + Doxycycline / Clindamycin OR Mefloquine / Malarone OR Quinidine gluconate
Gram-positive bacteria were inoculated under the skin of experimental animals and then the infection is treated with antibiotics. Bacteria isolated from the injection site several days later assume a spherical configuration when placed in an isotonic solution and disintegrate when placed in a hypotonic solution. Which antibiotic was most likely used in this experiment? A. Clindamycin B. Aztreonam C. Tetracycline D. Gentamicin
B. Aztreonam Bacterial morphology (shape) is determined by the cell wall. The bacteria described in this case lost their cell walls after antibiotic treatment, characterized by lack of osmotic instability (e.g. changes in shape and integrity under varying tonicity). This is most likely caused a loss of the cell wall. The bacteria were probably treated with a cell wall inhibitor (recall MOA of antibacterials). Choices A, C, and D are protein synthesis inhibitors and are unlikely to directly affect cell wall synthesis.
Alcohol-based hand sanitizers may be effective against the following organisms, except which one? A. Staphylococcus aureus B. Clostridioides difficile C.HPV16 D.Candida albicans
B. Clostridioides difficile There is concern because alcohol-based hand rubs are known to be less effective on soiled hands generally and, specifically, when there is C. difficile infection. This is because of the hand rubs' inability to kill the C. difficile spores that at times can be present. Alcohol is likely to eliminate all these microorganisms (A, C, and D), except clostridial spores.
PrP knockout mice, which are engineered not to express the PrP gene, show no obvious pathological phenotype. However, these mice have been shown to have abnormalities in all of the following, EXCEPT which one? A. Synaptic transmission B. Immunity C. Circadian rhythm D. Sleep
B. Immunity Since normal cellular prions (PrPc), sometimes called prion-like proteins (to differentiate them from the infectious prions), are involved in proper neurologic functioning, taking them out of the picture, e.g. through genetic knockout, can lead to neurologic impairment. By convention, immunity is, of course, not considered a neurologic function.
Which of the following is the OLDEST acid-fast staining method, which requires heating the specimen during the procedure? A. Fluorochrome B. Ziehl-Neelsen C.Kinyoun D.Auramine-rhodamine
B. Ziehl-Neelsen Remember: Ziehl-Neelsen - uses heat. It's zizzling! Kinyoun - is kold. Mycobacteria are extremely difficult to stain by ordinary methods because of the high lipid content of the cell wall. The phenolic compound carbol fuchsin is used as the primary stain because it is lipid soluble and penetrates the waxy cell wall. Staining by carbol fuchsin is further enhanced by steam heating (acts as mordant) the preparation to melt the wax and allow the stain to move into the cell. Acid is used to decolorize nonacid- fast cells; acid-fast cells resist this decolorization. The ability of the bacteria to resist decolorization with acid confers acid - fastness to the bacterium. Following decolorization, the smear is counterstained with malachite green or methylene blue which stains the background material, providing a contrast color against which the red AFB can be seen. The Kinyoun staining procedure is often referred to as cold carbolfuchsin because no heat is applied during the staining process unlike the Ziehl-Neelsen
All bacterial capsules are composed of polysaccharide EXCEPT?
Bacillus anthracis (polypeptide of D-glutamate)
DOC for Chloroquine- sensitive P. falciparum and P. malariae infections
Chloroquine
DOC for P. vivax and P. ovale infections
Chloroquine + Primaquine
An 18 year-old male presents with urethral discharge. You suspect he has a gonococcal infection. What is the gold standard for diagnosis? Urethral swab and Gram stain Culture of Chocolate agar with factor X and V Culture on Thayer-Martin medium Urinalysis
Culture on Thayer-Martin medium The gold standard test for the detection of Neisseria gonorrhoeae is culture, which has high sensitivity and specificity. However, it requires well trained staff and its performance is affected by specimen transport conditions. Other options include microscopy and tests that detect gonococcal antigen or nucleic acid.
There is a specific bacterial product that produces temporary relief of his esophageal symptoms in achalasia. Which agent produces this bacterial product? A. PrPres B. Clostridium tetani C. Rhabdovirus D. Clostridium botulinum
D. Clostridium botulinum
Combining drugs such as ampicillin and sulbactam circumvents which mechanism of bacterial resistance? a. Enzymatic inactivation b. Transpeptidase mutation c. Reprogramming of peptidoglycan precursors d. Mutation of DNA topoisomerases
Enzymatic inactivation Ampicillin is a beta-lactam drug that belongs to the penicillin group of antibacterials. It can be susceptible to breakdown by bacterial beta-lactamases (a.k.a. penicillinases). The addition of beta-lactamase inhibitors (e.g. sulbactam, clavulanic acid, tazobactam) can 'protect' the antibiotic from enzymatic hydrolysis and subsequent inactivation. For more info:
malaria DORMANT stage in the LIVER, pertinent only to P. VIVAX and P. OVALE, causes RELAPSE
HYPNOZOITE
Which of the following may be considered primarily responsible for the development of cellulitis from a small furuncle? Lipases Hyaluronidases Panton-Valentine leucocidins Hemolysins
Hyaluronidases Since hyaluronate is a major constituent of the ground substance of most connective tissues, particularly the skin, hyaluronidase may be an essential component in enabling the spread of the pathogens from an initial site of infection. Hyaluronidase is also known as the 'spreading factor.' e.g. A pimple today becomes cellulitis tomorrow!
A herd of cattle dies of anthrax. Anthrax is caused by the bacterium Bacillus anthracis, a spore-forming organism. To break the chain of transmission, which of the following is probably the BEST way to handle the carcasses of the cattle? Burying six feet below the ground Market sale and proper food preparation Incineration of the carcasses Treating the mass grave with antibiotic spray prior to burial
Incineration of the carcasses The preferred method of disposal of an anthrax carcass is incineration. Remember that Bacillus anthracis is a spore-former, and the spore confers protection and resistance to environmental stressors. It may also deter scavengers that would otherwise open up the carcass and thereby increase the contamination, and flies that might spread the disease.
host where parasite Harbors the asexual or larval stage
Intermediate Host
b-Lactam antibiotics act during this phase of bacterial growth
LOG OR EXPONENTIAL PHASE PHASE 1: LAG PHASE (notice the somewhat 'flat/straight' segment from the y-axis) Cells are depleted of metabolites as the result of unfavorable condition Adaptation to new environment Nutrients are incorporated Vigorous metabolic activity occurs but cells do not divide Zero growth rate PHASE 2: LOG OR EXPONENTIAL PHASE Rapid cell division occurs b-Lactam antibiotics act during this phase Constant growth rate Continues until either one or more nutrients in the medium become exhausted, or toxic metabolites accumulate and inhibit growth. PHASE 3: STATIONARY PHASE • Exhaustion of nutrients or the accumulation of toxic products cause growth to cease completely (zero growth rate) • Spores are formed PHASE 4: DECLINE OR DEATH PHASE • Most of the cells die because nutrients have been exhausted • Negative growth rate
A 24/M presents to his primary care physician with complaints of burning with urination. Three days later, the patient also has fever, skin flushing, and altered level of consciousness. PE: BP 60/40, HR 120/min. If blood cultures are positive for Klebsiella pneumoniae, which of the following bacterial factors is most likely responsible for this patient's current condition? A. Capsule B. Lipid A C. Peptidoglycan D. Flagellar antigen
Lipid A, a component of LPS in Gram-negative outer membrane, is sufficient to cause endothelial cell injury by promoting the expression of tissue factor and proinflammatory cytokines, leading to apoptosis of these cells. In a blood stream infection, presence of lipid A can lead to endotoxin shock (the clinical picture described in this vignette).
PROPHAGE-CODED BACTERIA
Lysogenized strains of ABCDE shigA - like toxin: EHEC Botulinum Cholera Diphtheria Erythrogenic toxin These toxins are produced by bacteria that have been infected by toxin- coding phages. Hence, lysogenized strains of these bacteria may actually produce toxins and cause disease. For example, if E. coli is lysogenized to contain the shiga-like toxin gene, then it gains more virulence, e.g. bloody diarrhea with hemolytic uremic syndrome. Ordinarily, E. coli can cause watery diarrhea; but bloody E. coli diarrhea must be a different pathogenic strain. This strain of lysogenized E. coli is called E. coli O157:H7, or enterohemorrhagic E. coli. In more re
malaria infective stage to RBCs
MEROZOITE
ONLY BACTERIA WITH MEMBRANE STEROLS
MYCOPLASMA
All bacteria have a cell wall composed of peptidoglycan except _________
Mycoplasma - Mycoplasma do not have cells walls!
OBLIGATE AEROBES
Nosy and Nagging Pests Must Breathe Lots of oxygen Nocardia Neisseria Pseudomonas Mycobacteria Bordetella/Brucella/B. cereus Legionella
Which component of the Gram-negative cell wall reduces its susceptibility to lysozymes? Teichoic acids Beta-lactamases in the periplasm M protein Outer membrane
Outer membrane The peptidoglycan layer in Gram-negative cells is 'sandwiched' between two membranes: an outer membrane and the plasma membrane (as an inner membrane). The outer membrane serves as a physical barrier that 'protects' the peptidoglycan immediately underneath from insult. Note that lysozymes result to cleavage of peptidoglycan glycosidic bonds: β 1→4 glycosidic bond between NAG and NAM.
Relapse - return of a disease after its apparent cessation (1-6 mos) due to reactivation of hypnozoites - seen in?
P. ovale and P. vivax
A 45/F consulted her physician for painless enlarging anterior neck masses accompanied by fever, chills, weight loss and malaise. Fine needle aspiration was done to rule out a malignancy. If the physician suspects TB lymphadenitis, which of the following should he request to RAPIDLY identify the mycobacterial species? PCR Culture on blood agar plate Ziehl-Neelsen staining Culture on Lowenstein-Jensen medium
PCR The PCR (polymerase chain reaction) method enables direct detection of infectious or parasite agents through enzymatic amplification of a part of their genome. This specific method can target and detect very weak quantities of pathogens in different types of samples. The question asks for a rapid, specific (key word: species) method, hence, PCR fits these criteria so well. Acid-fast staining (choice C) is rapid but not specific, while culture (choice D) takes weeks because the organism is grows slowly.
Extrachromosomal, double- stranded, circular DNA capable of replicating independently of the bacterial chromosome.
PLASMIDS
Which group of infectious agents does not require DNA as genetic material? Retroviruses Prions Bacteria Viroids
PRIONS The questions asks which one does not require. Even if prions are composed of proteins only, they still require genetic material to direct their synthesis. Remember: DNA makes RNA makes protein. This is the central dogma! The PRNP gene provides instructions for making a protein called prion protein (PrP), which is active in the brain and several other tissues.
host where parasite Parasite does not develop further to later stages
Paratenic Host
arthropod drugs moa Permethrin? Malathion? Lindane?
Permethrin: neuronal membrane depolarization via Na+ channels Malathion: acetylcholinesterase inhibitor Lindane: blocks GABA channels → neurotoxicity MOST effective scabicide; NEUROTOXIC for infants
a biochemical reaction in which antibodies bind to the bacterial capsule. The antibody reaction allows these species to be visualized under a microscope. If the reaction is positive, the capsule becomes opaque and appears to enlarge.
Quellung reaction - a.k.a. Neufeld reaction REMEMBER: QUELLUNG - CAPSULAR SWELLUNG!J
DOC for Uncomplicated infections with chloroquine- resistant P. falciparum
Quinine + Doxycycline or Clindamycin
malaria recurrence of symptoms after a temporary abatement (2-4 weeks) - seen in?
Recrudescence P. falciparum and P. malariae
Host where parasite Allow life cycle to continue and become additional sources of human infection
Reservoir Host
Which of the following molecular techniques represents a variation of the polymerase chain reaction, involving the use of an enzyme to convert viral RNA or messenger RNA to DNA prior to amplification? Reverse transcriptase PCR Real-time PCR Branched-chain DNA assay Southern blot
Reverse transcriptase PCR
malaria infective stage to HUMANS, also the infective stage to the LIVER
SPOROZOITE
A 38/M college professor complains of intense itchy, painful, red streaks between his fingers and in the groin area. The patient reports that the itchiness seems to be worse at night. He lives in an in-campus housing for University staff. Several of his housemates have presented with similar problems over the last couple of weeks.
Sarcoptes The most likely diagnosis here is scabies. Human scabies is caused by an infestation of the skin by the human itch mite (Sarcoptes scabiei var. hominis). The microscopic scabies mite burrows into the upper layer of the skin where it lives and lays its eggs. The most common symptoms of scabies are intense itching and a pimple-like skin rash. The scabies mite usually is spread by direct, prolonged, skin-to-skin contact with a person who has scabies. Its distribution in the finger webs, wrist, axillae, areolae, umbilicus, lower abdomen, genitalia, and buttocks is commonly referred as the circle of Hebra.
punctate granulations present in red blood cells invaded by P. ovale and P. vivax coarse granulations present in red blood cells invaded by P. falciparum fine dots present in red blood cells invaded by P. malariae
Schuffner Dots Maurer Dots Ziemann Dots Schuffner dots = P. Ovale & Vivax SOVrang daming dots! Maurer dots = coMMa-shaped = P. falciparum
Which of the following organisms lack membrane sterols? Yeasts Mycoplasmas Protozoa Staphylococci
Staphylococci Generally, bacteria do not have sterols in their membranes; but mycoplasmas are an exception. In fact, they are the only bacteria WITH sterols. The other groups have sterols, as follows: Protozoa and animals - cholesterol Fungi - ergosterol By now, remember that ergosterol is found in fungi. This molecule is a common target in antifungal therapy, e.g. ketoconazole inhibits ergosterol synthesis, amphotericin directly targets membrane sterols.
Code for drug-resistant enzymes, toxins, or metabolic enzymes Cause mutations in genes into which they insert (via a mutation) or alter the expression of nearby genes (e.g. causing the activation or repression of antibiotic resistance genes).
TRANSPOSONS a.k.a. "transposable" elements "Jumping genes"
BACTERIA NOT SEEN IN GRAM STAIN
These Rascals May Microscopically Lack ColorS Treponema (GIEMSA/ TISSUE STAINS) Rickettsia Mycobacteria (ACID-FAST STAIN) Mycoplasma (NONE (SEROLOGIES) Legionella (SILVER STAIN) Chlamydia (GIEMSA STAIN → INCLUSION BODIES) Spirochetes (DARKFIELD MICROSCOPY) (e.g. Spirochaeta, Treponema, Borrelia, and Leptospira)
gram staining procedure
V-I-A-S Violet Iodine Acetone Safranin
Prions are not normal and may cause disease because they exhibit a problem with which of the following? a. Folding of segments of polypeptide into geometrically ordered units b. Amino acid sequence in a polypeptide chain c. Protein assembly into the mature polypeptide and its component domains d. Number and types of polypeptide units of oligomeric proteins and their spatial arrangement
a. Folding of segments of polypeptide into geometrically ordered units
most common extraintestinal form of amebiasis? location? classic characteristic?
amebic liver abscess Usually in the posterosuperior aspect of the right lobe. This is according to majority of references. But according to Schwartz, it is the superior-anterior aspect anchovy sauce-like aspirate!!!
Lysozymes are enzymes that kill bacteria by cleaving which part of the cell wall? a. Pentaglycine bridges b. Multiple layers of peptidoglycan "net" c. β 1→ 4 glycosidic bond between NAG and NAM d. Tetrapeptide side chains
c. β 1→ 4 glycosidic bond between NAG and NAM Lysozymes destroy bacterial peptidoglycan by cleaving the β 1→4 glycosidic linkage between NAG and NAM. They are found in the secretions (tears) of the lacrimal glands of animals and in nasal mucus, gastric secretions, and egg white. Antibacterial mechanisms of lysozyme1. Hydrolysis of the β-1,4 glycosidic bond between the NAM of 1 monomer and the NAG of the adjacent monomer → hydrolysis of peptidoglycan leads to cell wall instability and bacterial cell death 2. Formation of pores by lysozyme (red cylinders) on the bacterial cell membrane → a mechanism involving its cationic nature; independent of peptidoglycan hydrolysis
A host where the parasite reaches sexual maturity.
definitive host
PATHOLOGY IN PRIONS
dysfunction due to protein misfolding 'Normal' prions have more alpha helices (they are normally expressed in neurons to aid in proper neuronal functioning). 'Pathological' prions suffer from a misfolding, where the beta sheets are produced. This misfolding makes pathological prions resistant to proteases, many chemicals, and normal autoclaving.
• Tissue Schizonticides o kill schizonts in the liver o EXAMPLE? • Blood Schizonticides o kill these parasitic forms only in the erythrocyte o EXAMPLES? • Gametocides o kills gametocytes in human blood o EXAMPLES? • Sporonticides o prevent sporogony and multiplication in the mosquito o EXAMPLES?
primaquine chloroquine, quinine primaquine proguanil, pyrimethamine
BUYS AT 30, CELLS for 50!
• 30s - Aminoglycosides, Tetracyclines • 50s - Chloramphenicol, macrolides (e.g. Erythromycin), Lincosamides (e.g. clindamycin), Linezolid, Streptogramins (e.g. dalfopristin / quinupristin)
