Micro Unit 4 (CH 12 & 13)

Viral infections of the lower respiratory tract

**INFLUENZA -Influenza is a highly communicable (easily transmissible) acute respiratory infection -it is enveloped, single stranded RNA virus -it's transmitted by airborne respiratory droplets -there have been at least 31 influenza pandemics since 1510 -the virion belongs to the Orthomyxoviridae family 1) Influenza A strikes every year & causes most epidemics 2) Influenza B also strikes every year but is less common than type A 3) Influenza C causes a mild respiratory illness but not epidemics -areas where birds, pigs, humans live closely together, can lead to antigenic shift -In most epidemics, birds & some mammals can serve as reservoirs for Influenza A -Spanish flue (1918) was the worst pandemic with about 50-100 million deaths

some human papillomavirus infections cause warts

**PAPILLOMA -benign, squamous epithelial growth, wart or verruca -caused by 100 different strains of HPV 1) Common seed warts- painless, elevated, rough growth; on fingers etc 2) Plantar warts- deep, painful; on soles of feet 3) Genital warts (condylomata) - most common STD in U.S. ; morphology ranges from tiny, flat, inconspicuous bumps to extensive, branching, cauliflower-like masses -are often transmitted through sexual contact (about 30-40 HPV types) -some strains of HPV are associated w/ cervical cancer -they may be transmitted to newborns during delivery -In 2006, the FDA approved Gardasil, a HPV vaccine -HPV types 16 & 18= 70% of cervical cancers -HPV types 6 & 11= 90% of genital warts -they can be transmitted by contact with: --->an affected person --->a contaminated object --->incubation- 2 weeks to more than a year

viral infections of the upper respiratory tract

**RHINOVIRUS -Rhinovirus infections produce inflammation in the upper respiratory tract -rhinoviruses belong to the Picornaviridae family -they are transmitted by airborne respiratory droplets or contact with contaminated objects -rhinoviruses are responsible for 30-50% of the cases of the common cold --->more than 200 different virus strains can cause common colds -researchers are studying the genome sequences for more than 100 rhinoviruses -looking for common sequences is helpful to develop a vaccine **ADENOVIRUS -adenovirus infections also produce symptoms typical of a common cold -it is a naked, double stranded DNA virus -some adenoviruses are frequent causes of acute upper respiratory infections -infections can cause: --->acute febrile pharyngitis --->pharyngoconjunctival fever --->acute respiratory disease (ARD) in military recruits (vaccine available) -many adenovirus infections progress to viral pneumonia -adenoviruses belong to the family Adenoviridae

Interesting link: Plague & HIV

-Bubonic plagues, caused by the Yersinia pestis bacterium, like HIV also attacks macrophages -a genetic mutation, CCR5-delta32, helped many Europeans survive the plague in the 17th century -descendants of those survivors that also carry the mutation, CCR5-delta32, are either protected against HIV, or cause the virus to progress more slowly -research is now being done on CCR5 inhibitors to mimic the mutation's effect for those afflicted w/ HIV

Invasive gastroenteritis

-Campylobacteriosis result from consumption of contaminated poultry or dairy products --->Campylobacteriosis is the most common cause of bacterial gastroenteritis in the U.S. -Campylobacter jejuni is transmitted through the fecal-oral route, usually by poultry -Gastric ulcer disease can be spread person to person --->Helicobacter pylori is involved in gastric ulcers --->it's unknown how H. pylori is transmitted, but it likely involves contaminated food or H2O --->the bacteria produce urease, which in turn produces ammonia --->ammonia neutralizes acid in that area of the stomach, allowing the bacteria to survive --->the ammonia & an H. pylori cytotoxin destroy mucous-secreting cells --->this creates a sore

Inflammatory gastroenteritis

-Cholera can involve enormous fluid loss ---> cholera is caused by Vibrio cholerae ---> V. cholerae are often consumed w/ raw oysters & H2O ---> the cells are susceptible to stomach acid ---> a large infectious dose is needed to colonize the intestines ---> cholera toxin (enterotoxin) causes unrelenting loss of fluid & electrolytes through diarrhea ( up to 1 L/hour) --->if untreated, fluid loss thickens the blood, leading to shock & coma --->antibiotics & restoration of H2O & electrolyte balance are effective in treatment --->vaccines using dead V. cholerae are available --->preventable by clean H2O & food -Clostridium difficile ---> Anaerobic, spore-forming, Gram (+) rod that occurs in soil, air, H2O, human & animal feces, & on most surfaces ---> causes diarrhea ---> major cause of pseudomembranous colitis (severe colon infection) ---> healthy people are resistant ---> at risk are elderly & those on antibiotics for extended periods ---> In 2008, new hypervirulent strain was found which was resistant to antimicrobials commonly used to treat C. difficile infections ---> fecal transplant can cure 90% of patients w/ severe, long-term C. difficile infections --->fecal transplant is accomplished via nasogastric or nasoduodenal tube, enema or colonoscope

Tetanus (soilborne bacterial disease)

-Clostridium tetani is a ubiquitous (found everywhere) soilborne microorganism that can cause tetanus, a disease characterized by toxin production & rigid paralysis -tetanus is preventable w/ appropriate immunization -treatment for acute tetanus is generally unsatisfactory, w/ significant morbidity (ie tetanus develops) and mortality (ie death) -Tetanus causes hyperactive muscle contractions --->spores can enter the body through a wound, and produce several toxins --->Tetanospasmin, a neurotoxin, will block the inhibition of muscle contractions ---> this leads to continuous, uncontrolled muscle contraction --->second most powerful toxin after the botulism toxin -symptoms of tetanus include: --->Trismus (lockjaw) involves spasms of the jaw muscle & clenching of the teeth --->Opisthotonus involves muscle spasms that cause an arching of the back --->Spasmodic inhalation & seizures in the diaphragm & rib cage (this reduces ventilation) -sedative (stop spasming of muscles), muscle relaxants (stop spasming of muscles), antitoxins (inactivate tetanospasmin) & penicillin (kills bacterial cells) are used in treatment -tetanus toxoid is used in vaccination --->DTap (diphtheria-tetanus-acellular pertussis) vaccine are given to children --->Booster injections of Td vaccine ("tetanus shot") or Tdap recommended every 10 years

viruses

-DNA viruses contain single or double-stranded DNA genomes -RNA viruses contain single or double-stranded RNA genomes ---> (+) strand RNA viruses have mRNA genomes ---> (-) strand RNA viruses have RNA strands that would be complementary to mRNA

Arthropoda

-Domain= Eukarya -Kingdom= Animalia -Phylum= Arthropoda -ex: spider, crabs, lobsters, millipedes, butterflies, bees, fleas, ticks, lice, mosquitoes, flies

Invasive Gastroenteritis- EHEC

-Enterohemorrhagic E. coli (EHEC) is often transmitted by undercooked ground beef (or bagged spinach) --->the most common form is 0157: H7 --->contamination also occurs in unpasteurized milk & juice, sprouts, lettuce, & salami --->infection can occur from contact w/ cattle or swimming in/ consuming contaminated H2O --->a small infectious dose causes hemorrhagic colitis 1-8 days after infection --->complications can occur in young children or the elderly, but most cases resolve in 5-10 days

Inflammatory Gastroenteritis- ETEC & EPEC

-Enterotoxigenic E. coli (ETEC) penetrate the intestinal epithelium & produce a toxin that causes gastroenteritis --->A.K.A traveler's diarrhea -Enteropathogenic E. coli (EPEC) cause diarrhea in infants, particularly where sanitation is lacking

Lyme disease (Arthropodborne bacterial disease)

-Lyme disease is one of the major emerging infectious diseases in the U.S. -causative agent is Borrelia burgdorferi which is transmitted by the bite of a small tick -there's a vaccine available for dogs, human vaccine was removed from the market Feb 2002 due to poor sales

other viral diseases of the skin

-Paramyxovirus infections can cause typical childhood diseases --->enveloped, single stranded RNA viruses **MEASLES (rubeola) -highly contagious disease caused by a member of the Paramyxoviridae family -transmission occurs through respiratory droplets -Koplik spots are red patches with white grain-like centers that appear along the gum line --->appear 2-4 days after the onset of symptoms -the characteristic red rash begins as maculopapules (flat red spots) at the hairline, spreading to the: --->face --->trunk --->extremities -complications include: --->bacterial disease in the respiratory tissue --->panencephalitis -vaccine is given in the measles-mumps-rubella (MMR) inoculation **MUMPS (infectious parotitis) -is characterized by enlarged jaw tissues caused by swollen salivary glands (near jaw/chin/cheeks) -the swelling is caused by blockage of ducts leading from the parotid glands -its spread by respiratory droplets or contact w/ contaminated objects -in males, swelling and damage may occur in the testes (orchitis)

Plague (Arthropodborne bacterial disease)

-Plague can be a highly fatal disease, killing around 25 million people in Europe during the middle ages -Yersinia pestis is spread by infected fleas carries on rodents

Virus-like agents

-Prions are infectious proteins -transmissible spongiform encephalopathies (TSEs) can occur in humans & other animals --->Ex: mad cow disease -TSEs are neurological degenerative diseases that can be transmitted within or between species -originally, scientists believed TSEs were caused by a virus -Stanley Prusiner discovered the proteinaceous infectious particle (prion) -the protein-only hypothesis predicts that prions are composed only of protein & contain no nucleic acids -normal cellular prions have a different shape than abnormal prions, the latter of which cause TSEs -The TSEs may spread when infectious prions bind to normal prions --->this causes normal prions to change shape & become abnormal -Abnormal prions DONT trigger an immune response -death of the host occurs from nerve cell death leading to sponge-like holes in brain tissue -symptoms include: --->dementia --->weakened muscles --->loss of balance -this results from insoluble aggregates of abnormal prions in the brain -the human form of TSE is called variant CJD (Creutzfeldt-Jakob disease)

Invasive gastroenteritis

-Typhoid fever involves a blood infection --->its caused by Salmonella enterica serotype Typhi (S. Typhi) -S. Typhi is transmitted by the 5 F's: 1) Flies 2) Food 3) Fingers 4) Feces 5) Fomites -S. Typhi is acid resistant --->it passes through the stomach to the small intestine --->it causes ulcers, bleeding, & pain -invasion of the blood can occur --->rose spots indicate blood hemorrhage -vaccines contain dead or attenuated S. Typhi or polysaccharides from S. Typhi capsule

Virus-like agents

-Viroids are infectious RNA particles that cause diseases in crop plants (including potatoes, citrus plants, coconut palms, and avocados) --->the replication cycle and disease causation process of viroids are not understood ---> one hypothesis suggests they originated as introns from mRNA processing

What is a virus (continued)

-Viruses have a host range & tissue specificity -a host range refers to what organisms the virus can infect -host range depends on capsid structure -many viruses infect certain cell or tissue types within the host (tissue tropism)

What is a virus (continued)

-a virion is a completely assembled, infectious virus outside its host cell -viruses are grouped by their shape: 1) Helical viruses have helical symmetry --->Ex: Tobacco mosaic virus & rabies 2) Icosahedral viruses have icosahedral symmetry --->Ex: Herpes simplex virus & poliovirus 3) Viruses that have both helical & icosahedral symmetry have complex symmetry are called complex viruses --->Ex: Bacteriophages & smallpox virus

Severe acute respiratory syndrome (SARS)

-affects the lower respiratory tract -enveloped, single stranded RNA virus -spreads through close person-to-person contact -SARS is an emerging infectious disease of the family Coronaviridae -It's spread by contact with an infected person or an object upon which they have coughed or sneezed -bats may be the natural host of the virus -a moderate upper respiratory illness may develop into severe respiratory illness & pnemonia -all SARS patients should be isolated for at least 10 days after fever has broken to prevent spread

Paramyxovirus affect the lower respiratory tract

-are all enveloped, single stranded RNA viruses **PARAINFLUENZA -parainfluenza infections are usually caused by human parainfluenza viruses 1 & 3 --->infections are milder than influenza **Respiratory syncytial (RS) disease -is caused by the respiratory syncytial virus (RSV) -it commonly affects children under 1 year of age -it infects the bronchials & alveoli of the lungs, causing cells to fuse together into syncytia **Human metapneumovirus (hMPV) -are RSV-like viruses -symptoms are milder than RS disease

Ehrlichial Infections (Arthropodborne bacterial disease)

-are emerging diseases in the U.S. w/ a tick vector -Ehrlichia species infect different groups of leukocytes (white blood cells) -Human monocytic ehrlichiosis (HME) ---> caused by Ehrlichia chaffeensis affect monocytes -Human granulocytic anaplasmosis (HGA) ---> caused by Anaplasma phagocytophilum affect neutrophils -HME & HGA symptoms are similar to Lyme disease but come & go more quickly ---> hard to diagnose because symptoms mimic other diseases, antibody detection will usually be negative in the first week of illness

inflammatory & invasive gastroenteritis

-bacterial GI infections have a longer incubation period than intoxications because bacterial cells must establish themselves in the body after ingestion -bacterial gastroenteritis often produces an inflammatory condition ---> dehydration is a common but serious complication of gastroenteritis

Tumors & Viruses

-cancer is an uncontrolled growth & spread of cells -a tumor is a clone of abnormal cells -normally, the body surrounds a tumor with a capsule of connective tissue --->a benign tumor -tumor cells can break free from the capsule & spread to other tissues of the body (metastasis) --->a malignant tumor -viruses are responsible for up to 20% of human tumors --->60-90% of human cancers are associated w/ carcinogens (environmental factor)

Epidemic typhus- typhus fever (Arthropodborne bacterial disease)

-caused by Rickettsia prowazekii -transmitted by body lice -its associated w/ war, famine, and poverty -patients have a high fever and rash ---> the macropapular rash starts on the trunk & progresses to the extremities ---> high fever, hallucinations, & delirium can occur -over 75% die in epidemics -w/ treatment this percentage is reduced, this disease is rare in the U.S.

Endemic typhus- murine typhus (Arthropodborne bacterial disease)

-caused by Rickettsia typhi -transmitted by fleas -symptoms are: ---> mild fever ---> headaches ---> maculopapular rash spreading from trunk to the extremities -recovery is spontaneous w/o the need of drug therapy

Gas gangrene (soilborne bacterial disease)

-causes massive tissue damage -gangrene occurs when blood flow stops to a part of the body -Clostridium perfringens produces a group of toxins & hydrolytic enzymes -skin usually turns red or black as the tissue dies due to lack of blood supply -spores enter the body through a severe open wound -vegetative cells ferment muscle carbohydrates & decompose muscle protein -dead tissue (myonecrosis) blocks blood flow causing gangrene & gas below the skin, the accumulated gas under the skin causes a crackling sound -while there are 12 exotoxins, the most important is α-toxin which damages & lyses blood cells -treatment involves: --->antibiotics --->tissue debridement (all dead tissue is removed) --->amputation ---> exposure in a hyperbaric oxygen chamber (high O2 concentrations)

The cultivation & detection of viruses

-detection of viruses is often critical to disease identification -Rivers' postulates expand upon Koch's postulates to help identify viruses --->filtrates of infectious material shown not to contain bacterial or other cultivatable organisms must produce the disease or its counterpart --->filtrates must produce specific antibodies -cytology uses light microscopy to examine cells for cytopathic effects (CPEs) of viral infection -occasionally, viruses can be observed directly by electron microscopy -cultivation & detection of viruses most often uses cells in culture --->in a primary cell culture, cells form a monolayer in a culture dish --->the type of cell culture depends on the virus to be cultivated in the monolayer --->viruses can be detected by the formation of plaques, a clear zone within the monolayer --->viruses can also be grown in fertilized eggs

Emerging viruses & viral evolution

-emerging viruses usually arise through natural phenomena --->emerging viruses may spread to new populations, or may expand host range --->genetic recombination can lead to "new" viruses --->mutation can occasionally be advantageous & create a new virus or strain of virus there are 3 hypotheses for the origin of viruses: 1) The regressive evolution hypothesis --->viruses are a result of an earlier life form that degenerated/reduced to only protein & genome 2) The cellular origins hypothesis --->viruses are derived from sub-cellular components & macromolecules that escaped from cell walls & replicated inside hosts 3)The independent entities hypothesis --->viruses coevolved w/ cellular organisms from a self-replicating molecule present on primitive earth

diseases of the skin caused by Herpesviruses

-enveloped, double stranded DNA virus -human herpes simplex infections are widespread & often recurrent **HSV-1 -cold sores are contagious sores caused by HSV-1 --->after primary infection, the viruses become latent (hidden) in sensory ganglia --->recurrence of cold sores occurs when viruses are reactivated and move to the epithelium **HSV-2 -genital herpes is a common STD, caused usually by HSV-2 -symptoms include: --->itching & throbbing in the genital area --->followed by blisters -spread through sexual contact -theres no cure, but antivirals can shorten and decrease the number of outbreaks -an individual can get HSV-1 & HSV-2 through sexual contact

Noninflammatory Gastroenteritis

-food poisoning illnesses are the result of enterotoxins -Staphylococcus aureus causes Staphylococcal food poisoning -incubation period is 1-6 hours -toxins are often consumed in protein-rich foods such as ---> meat & fish ---> dairy products -the enterotoxin (poison that acts GI tract) causes gastroenteritis for several hours -food is often contaminated by: ---> boils or abscesses on a handler's skin ---> through sneezing -proper handling, refrigeration, and heating help decrease the risk of contamination -Clostridium perfringens causes clostridial food poisoning ---> C. perfringens commonly contaminated meat, poultry, & fish ---> clinical symptoms require a high infectious dose & take 8-24 hours to appear -Bacillus cereus can cause diarrhea & vomiting ---> infections usually occurs from eating contaminated cooked grains

Take these everyday steps to protect your health

-get vaccinated -wash your hands often w/ soap & warm water, especially after you cough or sneeze -wash for 15-20 seconds -alcohol based hand wipes or gel sanitizers are also effective -cover your nose & mouth w/ a tissue when you cough or sneeze. Throw the tissue in the trash after you use it. If you dont have a tissue, cough or sneeze into your sleeve -avoid touching your eyes, nose, or mouth. Germs spread this way -avoid contact with sick people -if you get sick, stay home, dont infect others

Herpes keratitis

-infection of the eye --->it can cause scarring of the cornea & blindness -neonatal herpes is a threatening disease passed from infected mothers to newborns during childbirth --->the child's mental development can be delayed --->blindness & seizures can occur --->if genital herpes is present during childbirth, c-section is often performed

many foodborne and waterborne diseases have a bacterial cause

-intoxications: are illnesses in which bacterial toxins (can be dead toxins) are ingested with food & H2O -infections: are illnesses in which live bacterial pathogens are ingested & grow in the body

Leptospirosis (soilborne bacterial disease)

-is a zoonotic (the particular disease can be transmitted from vertebrate animals to people) disease found worldwide -Leptospirosis is carried by domestic & wild animals -Leptospira interrogans colonize the kidney of infected animals -the bacteria are passed through urine -humans acquire it by swimming in/ consuming contaminated H2O 1) the first phase involves flu-like symptoms and conjunctivitis 2) the second phase involves: --->fever --->meningitis --->lung & liver inflammation --->kidney damage --->vomiting of blood -when treated w/ doxycycline, mortality rate is low around 10%

Rubella (German Measles)

-is an acute, mildly infectious disease -its caused by a virus of the Togaviridae family -its transmitted by respiratory droplets or contact -symptoms of rubella include an occasional fever & pale-pink maculopapular rash -recovery is usually prompt, but relapses can occur -congenital rubella occurs when the fetus is infected through the placenta --->children may born with problems in the: eye, ear, heart

shingles (disease of the skin caused by herpesvirus)

-is an adult disease caused by the same virus as chickenpox -after infection, VZV can remain in nerve cells for many years -if they are reactivated, they can travel to the body trunk & cause blisters and patches of red -it can also cause facial paralysis and severe "ice-pick" pains -it can occur repeatedly -postherpetic neuralgia is the persistence of shingles pain for years after the blisters have disappeared -Zostavax is a vaccination to prevent shingles

Rocky Mountain Spotted Fever (Arthropodborne bacterial disease)

-is caused by Rickettsia rickettsii -transmitted by hard ticks -symptoms are high fever, headaches, and skin rash which spreads (it begins on the extremities & spreads to the trunk) -30% mortality rate w/o treatment -antibiotic treatment reduces this rate -mainly seen in Oklahoma, Arkansas, Texas

chickenpox (disease of the skin caused by herpesvirus)

-is no longer a prevalent disease in the united states -enveloped, double stranded DNA virus -a vaccine using attenuated viruses became available in 1995 -it's a highly communicable disease caused by the Varicella-zoster virus (VZV) -its transmitted by skin contact and respiratory droplets -a red, itchy rash spreads across the entire body and turns into fluid-filled vesicles which break open & yield highly infectious virus-laden fluid -the most common complication is bacterial infection of the skin

Yersinia pestis is still here (modern day)

-it's found today in the desert southwest among prairie dogs & other rodents -when plague is detected early, antibiotics like streptomycin or tetracycline can be used - a vaccine using dead Y. pestis cells is available to high-risk groups

Hantaviruses

-lower respiratory tract virus -enveloped, single stranded RNA virus -Bunyaviridae family -reservoir is a deer mouse, virus shed in saliva, urine, and feces -1-5 weeks after exposure symptoms of fatigue, fever, & muscle aches begin -can lead to respiratory failure as lungs fill with fluid -found in the desert SW in wet years -prevented by eliminating rodent nests

Foundations of virology

-many scientists contributed to the early understanding of viruses --->Dimitri Ivanowsky & Martinus Beiherinck studied the tobacco mosaic virus --->Walter Reed studied yellow fever & isolated the virus that caused it -In the 1930s, it was discovered that viruses are nonliving agents composed of nucleic acid & protein -with invention of electron microscope, by 1941, virologists were beginning to visualize viruses (virus range from 20-250 nm, smaller than eukaryotic cell: 10,000 nm, cell nucleus: 2800 nm, and bacteria: 2000 nm)

several ways food or H2O become contaminated

-meat= improper slaughter procedure -fruits/veggies- washed w/ contaminated H2O -infected humans handling food -cross-contamination -H2O- contamination -improperly stored foods

Clostridium botulinum (MOST dangerous intoxication)

-most dangerous foodborne intoxication -Botulism is caused by a neurotoxin that inhibits the release of the neurotransmitter acetylcholine preventing the contraction of muscles causing flaccid paralysis & respiratory arrest -treated by antitoxins & life-support systems like ventilators -prevented by heating foods before eating them for at least 10 minutes

Influenza (continued)

-name of virus includes the letter H & N and numbers --->the numbers have to do with special spike proteins on the surface of the influenza virus envelope -viruses contain 2 types of spikes 1) Hemagglutin (H) helps the virion attach & penetrate host cells 2) Neuraminidase (N) helps release virions from the host cell after replication & assembly -Hemagglutinin & neuraminidase antigens (will provoke immune response that creates antibodies) change with time -Tamiflu is a neuraminidase inhibitor --->when taken by an infected individual, it will block the influenza from exiting host cells, thereby halting the spread of the infection -different species harbor different strains of the flu virus --->ex: bird flu, pig flu, human flu --->pigs can be infected by avian (bird) & human strains and serve as a "mixing bowl" for new flu strains -a new flu strain evolves every year, antigenic shift, requiring development of a new vaccine- a mixture of the most common type A & B subtypes -complications such as pneumonia or secondary infections occur in: --->infants --->elderly --->immunocompromised people -influenza vaccine is comprised of multiple strains of influenza (usually 3-4) and usually are a mixture of Influenza A & Influenza B subtypes --->these mixture of strains are guessed by scientists and sometimes dont match the strains in the world. So, sometimes the vaccines are effective & sometimes not

the classification of viruses

-nomenclature & classification dont use conventional taxonomic groups -the International Committee on Taxonomy of viruses (ICTV) is developing a classification system -we will learn family names when we look at specific viruses -when naming, viruses will always have the suffix -viridae -names wont be italicized/underlined -Baltimore Classification system is also used (check notes)

Oncogenic viruses (virus that can cause tumors)

-oncogenic viruses transform infected cells -Epstein-Barr virus is linked to Burkitt Lymphoma, a tumor of the jaw -Human papilloma virus (HPV) is associated w/ cervical cancer --->there is now a vaccine against some HPV -the oncogene theory suggests that protooncogenes (before tumor genes) normally reside in the chromosomal DNA of a cell -protooncogenes can be transformed to oncogenes by: --->Uv radiation --->chemical carcinogens --->DNA damage --->viruses -sometimes a virus inserts its DNA (as a provirus) into a cell's chromosome next to a protooncogene --->when virus replication is triggered, the provirus replicates its DNA as well as a few adjacent host genes ---> V-oncogenes are protooncogenes captured in the viral genome --->when the oncogenic viruses infect another cell, the V-oncogene is under the virus' control, not the cell's control --->The V-oncogene can then code for growth factors, stimulating uncontrolled cell proliferation (rapid reproduction)

Invasive Gastroenteritis

-other Salmonella serotypes are often found in unpasteurized milk or poultry products & cause Salmonellosis -also associated with reptiles like: snakes, lizards, turtles -transmitted by the fecal oral route or they can also be transmitted by live animals -Shigellosis (bacterial dysentery) occurs where sanitary conditions are lacking --->Shigellosis is primarily caused by Shigella sonnei in the U.S. --->S. dysenteriae causes epidemics in the developing world --->contaminated foods commonly include eggs, vegetables, shellfish, dairy --->Shiga toxin (exotoxin) production in the intestinal epithelium triggers gastroenteritis --->infection of the large intestine can lead to fatal dysentery -no vaccine is available -E. coli diarrheas cause various forms of gastroenteritis --->Escherichia coli is normally found in the human intestine, but certain serotypes are pathogenic --->Transmission occurs through the fecal-oral route (via food/water)

Poxyvirus

-poxyvirus infections have had great medical impacts on populations -smallpox (variola) is contagious, and sometimes fatal --->macules= pink-red spots on the face & trunk --->papules= spots become pink pimples --->variola= pink pimples become fluid filled vesicles --->pustules= vesicles become deep pustules --->pocks= pitted scar when pustule breaks open and emits pus -vaccinations ceased in the U.S. in 1972 after eradication occurred, so many people are not immune -smallpox is one of the most dangerous weapons of bioterrorism

Animal virus

-some DNA viruses & retroviruses insert their genome into the host chromosome as a provirus -retroviruses use reverse transcriptase to transcribe their RNA to DNA -the provirus encodes a repressor protein that prevents activation of the viral genes necessary for replication -latent proviruses are immune to the host body's defenses --->they are propagated (multiplied) each time the cell's chromosome is reproduced

Structure and Indigenous Microbiota of the Digestive System

-the digestive system is composed of 2 separate categories of organs 1) Gastrointestinal (GI) tract 2) Accessory digestive organs -chemical, mechanical, and cellular defenses protect the GI tract from pathogen colonization -the human intestinal microbiome has not been well studied -NIH has launched the Human Microbiome Project to learn more about our gut microbiome -large intestine & mouth/oropharynx have largest amount of microbiota followed by small intestine & stomach -gram (+) microbiota found in: stomach, duodenum, jejunum, ileum, colon -coliforms found in: ileum & colon -anaerobes found in: ileum & colon

Oral Cavity (bacterial disease)

-the microbiota of mouth & large intestine represent extremely complex communities -oral diseases cause pain & disability for affected individuals -50-100 million bacterial cells inhabit the human mouth -dental plaque is a biofilm, containing salivary proteins, food debris, & bacterial cells & products -dental carries (tooth decay) results from : ---> plaque building ---> dietary carbohydrates ---> acidogenic bacteria -a major cause of dental carries is Streptococcus mutans & Streptococcus sobrinus ---> these acidogenic bacteria can ferment dietary carbohydrates into acids -Fluoride & diet can prevent dental carries ---> our H2O is fluorinated, fluoride strengthens our enamel which makes it harder for the acid products of microbes to penetrate our teeth ---> cutting out carbs can prevent dental carries -poor oral hygiene leads to increased subgingival plaque, which can be populated by bacteria -this can then progress to gingivitis & periodontal disease -periodontal disease is characterized by: ---> ulcers & bleeding along the gingival margin ---> degradation of periodontal ligaments & bone ---> loosened or lost teeth

viral replication & its control

-the replication of bacteriophages (HGT-transduction) is a 5-step process ---> T-even (Ex: T4, T6) group bacteriophages are virulent viruses that carry out a lytic cycle of infection in prokaryotes --->the phage nucleic acid contains only a few of the genes needed for viral synthesis & replication

clinical symptoms & duration of illness depend on

-the toxin or microbe -the infectious dose (amount of the toxin/microbe necessary to cause illness. This can vary based on age & demographics)

what are viruses?

-viruses are tiny infectious agents -viruses are small, obligate intracellular parasites (must get in the cell to multiply) -they lack the machinery for generating energy & large molecules -they need a host cell to replicate -the viral genome contains either DNA or RNA, but not both -the capsid is the protein coat, made up of capsomeres -the nucleocapsid is the capsid with its enclosed genome -some capsid proteins are spikes that help the virus attach to & penetrate the host cell -naked viruses are composed of only a nucleocapsid -viruses surrounded by an envelope (phospholipid bilayer stolen from previous host) are enveloped viruses -viruses can either be naked or enveloped, but not both

other forms of botulism

-wound botulism occurs when toxins are produced in anaerobic tissue of wounds -infant botulism is the most common form of botulism in the U.S. -it occurs when infants ingest endospores, commonly w/ honey, cause floppy baby syndrome -they are treated w/ Penicillin -Botulinum toxins are used in botox

Yersinia pestis causes several forms of the plague

1) Bubonic plague --->bacteria localize in the lymph nodes, in which hemorrhaging can occur forming buboes 2)Septicemic plague --->Bacilli can spread to the bloodstream from the lymph nodes, causing: 3)Plague meningitis --->from the bloodstream septicemic plague bacilli can spread to the meninges --->nearly 100% of untreated cases are fatal 4) Pnemonic plague --->septicemic cases can progress to the lungs allowing for human-human transmission through respiratory droplets to occur

Human forms of Anthrax

1) Inhalation anthrax: occurs in workers who work w/ animal hides and wool --->its also known as woolsorter's disease --->initially resembles common cold, can progress to severe breathing problems & shock --->its usually fatal if not treated early 2) Intestinal anthrax: occurs through consumption of contaminated, undercooked meat --->acute inflammation of the intestinal tract --->nausea, loss of appetite, vomiting, fever --->if untreated 25-60% of cases result in death 3) Cutaneous anthrax: occurs through contact of skin abrasions w/ spore- contaminated animal products (wool, hides, hair) --->A pustule of necrotic tissue forms (due to exotoxins), and lymph glands in the area may swell --->theres a cell-free vaccine available to people who work w/ livestock --->Anthrax was an agent of bioterrorism through the mail in the U.S. in 2001

inflammatory gastroenteritis (continued)

1) Listeria monocytogenes causes listeriosis through fecal contaminated food, water, & milk -it primarily affects pregnant women, newborns, elderly, & the immunocompromised causing a form of meningitis 2) Brucella sp. cause brucellosis from contaminated animal products through a cut in the skin -this is called undulant fever (rising & falling fever) -both can be prevented by pasteurization -sheep, cattle, goats, & pigs are commonly infected 3) Vibrio sp. causes seafood borne gastroenteritis

Levels of Gastroenteritis

1) Noninflammatory Gastroenteritis- diarrhea and/or vomiting, no fecal leukocytes, no blood in stool, usually no fever 2) Inflammatory Gastroenteritis- diarrhea and/or vomiting, fecal leukocytes present, usually see fever, no blood in stool 3) Invasive Gastroenteritis- invasion past epithelial layer of GI tract, may not have any diarrhea or vomiting, dysentery may be present (mucous containing bloody feces), fecal leukocytes present, blood in stool, fever, may not have any GI tract problems but instead see systemic problems

Animal virus replication in a productive infection

1) Phase 1: Attachment to host plasma membrane via spikes on the capsid or envelope 2) Phase 2: Penetration-since receptor sites vary from person to person, some people are more susceptible to a certain virus than others --->Animal viruses are usually taken into the cytoplasm as intact nucleocapsids --->spikes on enveloped virus bind to membrane receptors & fuse. The nucleocapsid will enter into the cytoplasm where uncoating will occur -naked viruses bind to membrane receptors & the nucleocapsid will enter cytoplasm as vesicle & then will go through uncoating -uncoating is the separation of the capsid from the genome 3)Phase 3: Biosynthesis is when the viral genome takes over the animal cell & directs it to make viral proteins & more viral genomes 4)Phase 4: Maturation where all the parts made in phase 3 are assembled to make fully formed virus particles, takes place in nucleus 5)Phase 5: Release- after the new viruses are assembled, envelope proteins are incorporated into a cellular membrane --->the virus buds, taking the membrane part with it as an envelope

5 phase bacteriophage replication

1) Phase 1: Attachments occurs when a phage's tail fibers match with a receptor site on the bacterium's cell wall 2)Phase 2: Penetration occurs when the phage tail releases lysozyme to dissolve a portion of the cell wall --->phage DNA is injected into the bacterial cytoplasm 3)Phase 3: Biosynthesis is the production of new phage genomes & capsid parts 4) Phase 4: Maturation is the assembly of viral parts into complete virus particles 5) Phase 5: Release is the exit of virions (fully formed infectious virus thats outside host cell) from the bacterium --->it's also called the lysis stage when the cell is ruptured -temperate phages dont lyse the host --->they insert their DNA into the bacterial chromosome as a prophage (lysogenic cycle: phage DNA hides in the host chromosome)

Stages of Lyme Disease

1. Early localized stage: 3-31 days post tick bite --->A bull's-eye rash begins at the site of the tick bite w/ fever, aches, & pains & flu-like symptoms 2. Early disseminated stage: weeks to months post tick bite ---> if untreated, it can spread to skin, heart, nervous system, and joints 3. Late stage: months to years post tick bite --->develops chronic arthritis & swelling in the joints -treatable by antibiotics in early stages

Rickettsial & Ehrlichial Arthropodborne disease

Rickettsia infections often involve a characteristic rash & tick, lice or flea vectors

Borrelia burgdorferi life cycle

Year 1: 1) female lays egg in environment 2) Early summer: eggs hatch in soil, larva emerge 3) Mice are a main reservoir, if a tick feeds on infected mice, it becomes infected 4) Winter: infective larva leave mice for dry leaves Year 2: 5) Spring: infected larva become nymphs 6) Infected nymphs feed on animals or humans & transmit disease 7) Early fall: infected nymphs become adults 8) Late fall: adults feed in fur of deer & mate to complete the cycle

Neurotoxin

a poison that acts on the nervous system

Antitoxins

are produced by the host body and neutralize (inactivates) toxins

retroviruses (notes)

are required indirectly through a DNA intermediate using an reverse transcriptase enzyme --->use RNA as a template to make DNA

Toxoids

are toxins whose toxicity has been destroyed but still elicit an immune response ("memory cells")

extremities

hands and feet

Soilborne bacterial diseases

includes anthrax, tetanus, gas gangrene, & Leptospirosis Anthrax -is an enzootic (endemic (always present at low levels) to populations of animals) disease of large herbivores that ingest the spores while grazing -Bacillus anthracis produces a capsule & 3 exotoxins

outbreak

is a more contained epidemic

pandemic

is a worldwide epidemic -Ex: ebola & covid-19

endemic disease

is habitually present at a low level in a certain geographic area

Toxigenicity

is the ability of pathogens to produce toxins

Toxemia

is the presence of toxins in the blood

tissue tropism

is usually due to specific cell surface receptors being present on the host cell that the virus can bind to & use as an entry point to invade the host cell

Baltimore classification system

look at notes

demographics can

make individuals more or less prone to food/waterborne illness -ex: age or sanitary conditions

epidemic disease

occurs in a region in excess of what is normally found in that population

Enterotoxins

poison that acts on the gastrointestinal tract

Cytotoxins

poison that acts on the specific cells

Endotoxins

poison that is part of bacterial cell wall

Exotoxins

poison that is secreted from bacteria

antigenic shift

rapid major change in what antigens are on the virus

incubation period

time between consumption of contaminated material and appearance of symptoms

toxoid

toxin thats been altered, stimulated immune system but isnt poisonous

serotype

when antibiotics are applied in a serological technique, this specific strain will have antigens that are recognized by the specific serological antibodies