Microbes and diseases: what to study-1

1. Microbes and diseases: what to study-1 • 1. Causative microbe: name, morphology (shape, size, Gram stain, etc.), physiology (aerobe, anaerobe, etc) and some info on classification (what's it related to?) • 2. Pathogenesis and clinical disease:  what disease does it cause (signs and symptoms) and how does it do it (capsule, toxins..)? • 3. Transmission and epidemiology: how do you get the disease?

2. Microbes and diseases: what to study-2 • 4. Diagnosis: How does the lab usually identify the causative agent? • 5. Treatment: antibiotics prescribed (or not- no cell wall, no penicillin) or other treatment (oral rehydration therapy for cholera). • 6. Prevention and control (stop the spread; condoms, kill urban rats..)

3. Staphylococcus: G+ coccus • S. aureus and S. epidermidis. • S. aureus much worse, S. epi an opportunist. • Sturdy, salt tolerant, fac anaerobes; clusters • S. epidermidis common on skin, S. aureus less. • Diseases of S. aureus • Food poisoning, skin diseases (impetigo, folliculitis, furuncles & carbuncles, scalded skin syndrome), systemic diseases (TSS, bacteremia, heart, lung, and bone infections) • Diseases spread by fomites and direct contact.

4. Characteristics of S. aureus infections tray.dermatology.uiowa.edu/ DIB/SSSS-002.htmwww.omv.lu.se/.../ rorelse/popup/01d1x.htm

5. S. aureus virulence factors & Rx • Coagulase, triggers blood clotting. • Capsules, beta-lactamases (destroy penicillins) • Toxins: various, including TSS toxin, exfoliatin, and enterotoxins (heat stable) • 95% resistant to penicillin, but now many resistant to methicillin, oxacillin. Treatment usually clindamycin (oral) or vancomycin (IV). http://www.biology4kids.com/extras/dtop_micro/7821_580.jpg

6. Streptococci: G+ cocci • Genera: Streptococcus and Enterococcus • Aerotolerant anaerobes, catalase negative • Grow in chains, pairs • Strep: Lancefield groups, viridans, S. pneumoniae • Group A strep: S. pyogenes • Pharyngitis, scarlet fever, pyoderma, erysipelas, TSS, necrotizing fasciitis • Sequelae: rheumatic fever and glomerulonephritis http://genome.microbio.uab.edu/strep/info/strep5.gif

7. Characteristics of Streptococcal infections http://euclid.dne.wvfibernet.net/~jvg/Bio208/resp_pix/scarlet-fever.jpg http://textbookofbacteriology.net/vvpath.jpeg

8. Virulence factors, etc. • S. pyogenes (“pus-producing”) • M protein and capsule: avoids phagocytosis • Streptokinase, streptolysins for escape & attack • Pyrogenic erythrotoxins (SPEs) • at least 3 different types • Cause scarlet fever: fever, rash; toxic shock • Beta hemolytic on blood agar • Viridans group: greenish alpha hemolysis • Common in throat, mouth, but can be opportunists • S. mutans associated w/ dental caries

9. Clostridium: G+ rods • Strict anaerobes! Endospore formers. Toxigenic • Common in soil, sewage animal GI tracts • Produce neurotoxins, enterotoxins, histolytic toxins • Four important species: C. perfringens, C. botulinum, C. tetani, and C. difficile. • C. perfringens • Food poisoning: cramps and diarrhea • From injury: myonecrosis to gas gangrene • Fermentation in tissues, killing of tissues and spread of cells into anaerobic areas. • Oxygen treatment, debridement, amputation

10. More clostridia • C. difficile: normal GI microbiota • Cause of pseudomembranous colitis, resulting from overgrowth following broad spectrum antibiotics • Damage to GI wall can lead to serious illness • Nosocomial infection, easily transmitted • C.botulinum: cause of botulism • Usually acquired by ingestion: intoxication • Food borne, infant (no honey), wound • Produces neurotoxin, inhibits acetylcholine release • Flaccid paralysis; Botox: deadly poison / beauty • Mouse bioassay; administer antitoxin

11. Opposing muscle groups When biceps contracts, triceps relaxes. When triceps contracts, biceps relaxes. Excitatory neurons send signal to contract, inhibitory neurons send signal to NOT contract. http://upload.wikimedia.org/wikipedia/sv/thumb/d/dd/185px-Muscles_biceps_triceps.jpg

12. Function of nerves http://upload.wikimedia.org/wikipedia/fr/thumb/e/e4/200px-Synapse.png http://www.people.virginia.edu/~dp5m/phys_304/figures/motor_unit.jpg

13. More clostridia-2 • C. tetani: cause of tetanus • Growth in anaerobic wounds, makes tetanus toxin • Toxin prevents action of inhibitory neurons • Opposing muscle pairs both contract • Spastic paralysis, leading to death. • Recommendation is booster shot every 10 years • DPT, Toxoid vaccine • Booster: DT (with diphtheria toxoid) • No natural immunity: you would die first.

14. Mycobacterium: G+ rods • Many non-pathogenic species, most disease: M. tuberculosis and M. leprae • Mycolic acids as part of complex cell wall • Protects against desiccation • Protects against destruction by phagocytes • Requires acid-fast staining • Generally grow very slowly (chronic illnesses) • Can grow intracellularly

15. Acid Fast stain of Mycobacteria http://www.md.huji.ac.il/mirror/webpath/AIDS071.jpg

16. M. tuberculosis • Causes disease tuberculosis, mostly lung dis. • Disease: cells enter lungs, infect macrophages • Macrophages not activated, can’t kill invader • Cell mediated immunity fights back, walls off infection; forms tubercle (caseous necrosis occurs) • Disease remains controlled, cured, or returns • Disseminated TB: spreads thru body • Worldwide problem; lowered immunity=risk • Skin test, chest x-ray, drug treatment, vaccine?

17. M. leprae • Cause of Hansen’s disease, aka leprosy • Slow growing, likes it cool; armadillos as model • Grows in peripheral nerve and skin cells • Numbness is characteristic of disease • Tuberculoid vs. lepromatous leprosy • Mild, severe, respectively, depending on cell mediated immune response. • Numbness vs tissue destruction • Spread mostly by direct contact • Treatable with antibiotics, but long term

18. Gram negative rods and cocci • Endotoxin: Lipid A, the superantigen • Part of LPS of the Gram negative outer membrane • Causes an over-stimulation of macrophages with production of various cytokines • Fever, vasodilation, inflammation, shock, and disseminated intravascular coagulation • While Gram negative pathogens can have other virulence factors (capsules, fimbriae, exotoxins), all have endotoxin and are thus dangerous.

19. Enterobacteriaceae: Gram negative rods • Gram negative, small rods, facultatively anaerobic, oxidase negative; found in soil, water, and GI tracts • some strictly pathogens, others opportunists • Coliforms (ferment lactose) and non-coliforms • Virulence factors • Endotoxin, capsules, fimbriae, exotoxins, others. • Enteric bacteria identified by biochemical tests • Selective/differential media, IMViC tests, etc. • Strains identified by serological techniques

20. Serology and enteric bacteria • Because enteric bacteria are very closely related to each other, differentiation requires serology • Use of antibodies to identify particular antigenic molecules on cell surfaces • O antigen: repeating sugar group on LPS • H antigen: flagellar protein • K antigen: capsule antigen around cell. • Example: E. coli O157:H7 describes particular serotype which happens to also produce a dangerous exotoxin.

21. http://www.ratsteachmicro.com/Assets/Enterobacteriaceae/Enterobact_diagram2.gifhttp://www.ratsteachmicro.com/Assets/Enterobacteriaceae/Enterobact_diagram2.gif

22. E. coli: friend or foe? • E. coli: cause of 90% of urinary tract infections • Most strains common to GI tract, not harmful there. • Strains have fimbriae needed for attachment • Proanthocyanidins in cranberry juice interfere • E. coli: common cause of diarrhea • Many strains possess genes (some on plasmids) that code for additional virulence factors like exotoxins which cause disease • E. coli O157:H7: possesses shiga toxin; strain causes hemolytic uremia syndrome, damages kidneys. • E coli strains classified as EHEC, EIEC, EPEC, etc. • Enterohemorrhagic, enteroinvasive, etc.

23. Truly pathogenic enterics • Salmonella: species so closely related that they are really all S. enterica. But medically, species epithets still used: S. typhi and others. Divided serologically. • Present in eggs, poultry, on animals such as reptiles • Large dose results in food poisoning; diarrhea, fever, etc. • Cells phagocytized by intestinal lining cells, kill cells causing symptoms, may pass through into blood. • S. typhi: typhoid fever. Spread through body • Gall bladder as reservoir; Typhoid Mary • Importance of clean water and sewage treatment. • http://www.newsday.com/community/guide/lihistory/ny-history-hs702a,0,6698943.story

24. Truly pathogenic enterics-2 • Shigella: especially S. sonnei (most common) and S. dysenteriae (most serious); cause shigellosis. • Food, flies, fingers, feces, fomites: very small infectious dose, personal hygiene important in prevention. • Infection of intestinal lining damaged, cells pass directly from cell to cell; cramps, diarrhea, bloody stools. • S. dysenteriae produces shiga toxin which inhibits protein synthesis, increases damage. • Most serious problem with diarrheal diseases in general is dehydration.

25. Truly pathogenic enterics-3 • Yersinia: Y pestis is cause of plague, other species cause food-borne infections • Plague: 3 cycles: sylvan, urban, and human • endemic in sylvan cycle; mixing of woodland and urban rodents brings urban cycle, fleas jump from dying rats to humans. • Infection leads to large swollen lymph nodes: buboes • Bubonic plague, with high fever. • Septicemic plague: with DIC, bruising (black death) • Raises mortality from75% to near 100% • Pneumonic: coughed out and spread human to human • 100% mortality

26. The S.F. earthquake and plague http://library.thinkquest.org/03oct/00904/images/sanf.jpg http://www.cdc.gov/ncidod/dvbid/plague/plagwest.htm

27. Other Gram - rods • Francisella: F. tularensis, cause of tularemia • Also called rabbit fever, tick fever, deerfly fever, etc. • Most cases in US in Arkansas/Missouri Ozarks • Survives phagocytosis, lives intracellularly • Present in many animals, transferred to humans by vector, ingestion, direct contact, inhalation • Chills, fever, malaise, swollen nodes http://er1.org/docs/photos/Tularemia/Amblyomma%20Americanum%20(lone%20star%20tick).jpg http://mercury.bio.uaf.edu/~george_happ/Francisella.jpg

28. Other Gram – rods-2 • Legionella: L. pneumophila and several others • Fastidious in culture, requires special media • Very common in aquatic environments: ponds, cooling towers, hotwater heaters, showers. • Grows normally in amoebae, so also grows in phagocytes • Most dangerous as opportunistic pneumonia, inhalation • Mild form of disease: ‘pontiac fever’ www.angelfire.com/.../ bicentennial.html

29. Chlamydia • Very small, obligate intracellular parasites • Cell and outer membrane, but no peptidoglycan • Spread directly rather than by vectors • Two stage life cycle • Elementary body: tiny (0.2-0.4 µm) and inert • Spore-like: dormant and resistant • Infectious: form that moves between cells • Reticulate body: 0.6-1.5 µm, metabolically active, reproduce inside host cells

30. Chlamydial diseases • C. trachomatis: infects cells of mucous membranes, conjunctiva. Mostly eye & STD • Infection kills cells, stimulates inflammation which also causes cell destruction • Trachoma- leading cause of non-traumatic blindness. Caused by certain strains. • Infection of conjunctiva causes scarring, turning in on eyelashes which scratch cornea. • Scarred cornea, with ingrown blood vessels, obscure vision. • STD strains can also infect eyes, self-inoculation.

31. Sexually transmitted Chlamydial disease • Non-gonococcal urethritis, about 50% of cases • Chlamydia infections are the most common STD, but even more are infected and asymptomatic • 85% of women asymptomatic; others can develop PID; scarring of uterine tubes can lead to sterility, ectopic pregnancy. • Eye infections of newborns prevented with antibiotic drops. • Also protects against N. gonorrhoeae

32. Gram negative curved rods • Vibrio: comma shaped • Like enteric but oxidase positive; polar flagella • Halotolerant to halophilic, grow in estuarine and marine environments • V. cholerae: cause of cholera • Toxin-mediated severe diarrhea • Salt, fluid leave intestinal cells, patient dies of dehydration. • Oral rehydration therapy (ORT): water, salts, and glucose, now saving lives. • Causes pandemics that spread around the world • Lack of adequate sewage treatment

33. Campylobacter • Campylobacter jejuni: number one cause of bacterial gastroenteritis; zoonotic • More common than Salmonella and Shigella combined for food borne disease. • Most retail chickens are contaminated; improperly cooked chicken and contaminated milk typical vehicles. • Low infectious dose • Gram neg. curved rod http://www.shef.ac.uk/staff/newsletter/vol23no10/images/campylobacter.gif

34. Helicobacter pylori • Cause of ulcers and gastritis • 2005 Nobel Prize for Medicine or physiology to Barry Marshall and J Robin Warren • Unusual because it can live in stomach • Produces urease enzyme • Released ammonia neutralizes stomach acid, irritates stomach lining. • Basis for radioactive urease test. • Correlated with stomach cancer. http://s99.middlebury.edu/BI330A/STUDENTS/KASSIS/images/pylori1b.jpg