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H. pylori - virulence factors
- Flagella: corkscrew motility enables penetration into viscous environment (mucus)
- Mucinase: degrades gastric mucus
- Urease: producing ammonia and neutralizing gastric acidity
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Food intoxication
- Intoxication=toxins (or poisons) not bacteria cause illness
- Staphylococcus aureus
- Bacillus cereus
- Clostridium perfringens
- Clostridium botulinum
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Food Infection
- bacterial proliferation
- Listeria monocytogenes
- Escherichia coli
- Salmonella
- Shigella
- Yersinia enterocolitica
- Vibrio
- Campylobacter
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S.aureus
- GPC, nosocomial, cutaneous most common infection
- Enterotoxin (heat stabile)
- mainly responsible for staphylococcal food poisoning
- heat stable (100°C, 30 min)
- act as superantigen
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Bacillus cereus
- GPB, ubiquitous in soil
- Emetic-Rice, vomit, HEAT-STABILE
- Diarrheal-meat, veggies, diarrhea, HEAT-LABILE
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Clostridium
- GPR, spore-formers
- ubiquitous in soil, water, normal flora in GI
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C. perfringens
- Heat-labile enterotoxin
- meat, sauces, gravy
- Gastroenteritis
- Spore is heat stabile
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C. botulinum
- botulinum toxin
- home-canned foods, honey
- Botulism (paralytic illness)
- spore is heat resistant
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Listeria monocytogenes
- GPR, non-spore
- isolated habtats
- refrigerator and preserved food
- Listeriosis
- facultative intracellular
- Low temp, high salt
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facultative intracellular food poisoners
- Listeria
- Enteroinvasive E.coli (EIEC)
- Salmonella
- Shigella
- Yersinia
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Enterobacteriaceae Food infectors
- Escherichia coli
- Salmonella
- Shigella
- Yersinia enterocolitica
- facultative anaerobes
- catalase +
- oxidase -
- capsule
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Escherichia coli
- Most common aerobic gram-negative rods in the GI tract
- Strains causing gastroenteritis are generally acquired exogenously (contaminated food and water).
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E.Coli Gastroenteritis toxins
- Shiga toxins (Stx) 2A/5B - hemolytic uremic syndrom-enterotoxin effect-block uptake of electrolytes
- Shiga-like toxins
- Heat-labile enterotoxins (LT) - (cholera same action) inc cAMP and andenylate cyclase which causes hypersecretion of water and electrolytes
- Heat-stable enterotoxins (ST)
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EAEC
- enteroaggregative
- non-nvasive
- ST-like toxin and hemolysin
- lethal to intestinal epitelial
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ETEC
- Enterotoxigenic
- non-invasive(no-fever)
- LT and/or ST (heat labile, heat stabile)
- traveler's diarrhea
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EPEC
- moderately invasive "attaching-effacing"
- strips microvilli->osmotic diarrhea
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EHEC
- moderately invasive "attaching-effacing"
- Stx
- hemmorhagic colitis maybe hemolytic uremia
- E. coli O157:H7 (verotoxin = shiga toxin)
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EIEC
- Enteroinvasive E. coli (EIEC)
- invasive
- type III secretion
- dysentery-like diarrhea
- FEVER
- potentially fatal
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Salmonella
- primary pathogen (always disease)
- poultry eggs
- fecal-oral
- bile salt tolerant
- intracellular
- LT (heat labile enterotoxin)
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Shigella
- primary pathogen
- polluted drinking water
- fecal-oral
- highly infectious
- S. dysenteriae
- Shigellosis=bacillary DYSENTERY-blood, white cells, intestinal sloughing
- intracelluar
- bile resistant
- STX-A-ribosome
- blocks uptake of electrolytes
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Yersinia
- Y. pestis-black death
- Y.enterocolitica-pork
- intracellular
- TYPE III
- low temp
- Gasteroenteritis
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Vibrio
- GNR-motile
- Vibrio cholerae
- Vibrio parahaemolyticus (halophilic)
- Vibrio vulnificus (halophilic)
- salty shellfish
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Vibrio cholerae
- contaminated water or food.
- person-to-person spread is rare
- killed by stomach acids
- Cholera enterotoxin (CtxA, CtxB)->andeylate cyclase->cAMP->hypersecretion (same as LT)
- "rice-water stool"
- Death caused by dehydration
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Campylobacter jejuni
- MOST COMMON DIARRHEA IN US (Campylobacter, Salmonella, Shigella, E.Coli)
- GNR
- penetrate mucus barrier with a corkscrew motion.
- Most common cause of bacterial diarrhea in US, mostly via ingestion of animal sources especially chickens
- Pathogenesis not fully characterized
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Clostridium difficile
- Not a food-poisoning pathogen
- Normal intestinal flora in a small proportion of healthy individuals (5%)
- Diseases (side effects of taking antibiotic medicine)
- antibiotic associated diarrhea (AAD)
- antibiotic induced pseudomembranous colitis
- Virulence factors
- exotoxin A: increases permeability of the intestinal cell wall (diarrhea)
- exotoxin B (cytotoxin): damage mucosa and cause pseudomembrane formation
- Exposure to antibiotics is associated with overgrowth of C. difficile and subsequent GI diseases
- antibiotic associated diarrhea (AAD)
- antibiotic induced pseudomembranous colitis
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