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Gastrointestinal Tract Infections

Noninflammatory Gastroenteritis- food poisoning (click on organisms for more detail)
Staphylococcus aureus Various Mushrooms 
Bacillus cereus
Clostridium perfringens
Clostridium botulinum  
Inflammatory Gastroenteritis (click on organisms for more detail)
Vibrio cholerae Rotavirus Giardia lamblia (intestinalis)
Enterotoxigenic (ETEC) E. coli Norwalk Agent Cryptosporidium parvum
Enteropathogenic (EPEC) E. coli Noroviruses Cylospora cayetanensis
Enteroaggregative (EAggEC) E. coli
Clostridium difficile
Vibrio parahemolyticus
Bacillus anthracis
Invasive Gastroenteritis(click on organisms for more detail)
Shigella sp. Entamoeba histolytica
Salmonella sp.
Campylobacter jejuni
Enteroinvasive E. coli (EIEC)
Enterohemorrhagic E. coli (EHEC)
Vibrio vulnificus
Yersinia sp.
Francisella tularensis
Helicobacter pylori
Noninflammatory Gastroenteritis- diarrhea and/or vomiting, No fecal leukocytes, no blood in stool, usually no fever.

Inflammatory Gastroenteritis- diarrhea and/or vomiting, fecal leukocytes present, usually see fever, no blood in stool.

Invasive Gastroenteritis- invasion past epithelial layer of GI tract, May not have any diarrhea or vomiting, dysentary 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.

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Microbial Agent
 Mode of Transmission
Microbial Toxins Responsible
Disease and Classic Feature
Noninflammatory Gastroenteritis- food poisoning
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Staphylococcus aureus-gram positive coccus Ingestion; Food poisoning; mayonnaise containing and/or dairy products Heat stable enterotoxins; 5 types labelled A, B, C, D, E. Enterotoxins cause 5-hydroxytryptamine (serotonin) to be released in the intestine, which then binds to 5-hydroxytryptamine receptors on vagal afferent neurons and causes emesis. Vomiting, little or no diarrhea, no fever
Bacillus cereus-gram positive rod Ingestion; Food poisoning Type 1: emetic form; heat-stable enterotoxin is called depsipeptide cereulide. Mechanism for vomiting is unknown. In rare cases of liver failure the enterotoxin uncouples oxidative phosphorylation in liver mitochondria.
Type 2: diarrheal form; heat-labile enterotoxin; stimulates adenylate cyclase (increases cAMP)
Type 1: starchy food= vomiting; little diarrhea; no fever
Type 2: meats and cream sauces= diarrhea; little vomiting; no fever
Clostridium perfringens-gram positive rod Ingestion; Food poisoning A single heat-labile protein of 34,000 molecular weight inhibits glucose transport in intestinal epithelial cells, damages the intestinal epithelium and causes protein loss into the intestinal lumen. This activity is maximal in the ileum and minimal in the duodenum diarrhea; little or no vomiting; no fever
Clostridium botulinum-gram positive rod Ingestion; Food poisoning; canned foods;
In newborns ingestion of honey
Protein of 150,000 molecular weight that prevents release of acetylcholine at the     neuro-muscular junction causing a flaccid paralysis; 8 distinct antigenic types labelled A, B, C1, C2, D, E, F, G Botulism; flaccid paralysis of muscles; ptosis of eyelids, facial muscle paralysis.
Various conditions due to ingestion of poisonous mushrooms
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Mycetismus gastrointestinalis  Ingestion of  mushroom. violent retching
and diarrhea accompanied by cramps
Mycetismus choleriformis Ingestion of  mushroom amanitine and muscarine long symptomless period (6-24 hours) following ingestion. The symptoms begin suddenly and are characterized by violent vomiting, continuous diarrhea, dehydration and muscle cramps.
Poisoning is diphasic. Symptomatic treatment results in remission; however, there is often a fatal relapse. The terminal symptoms include a sudden onset of confusion, comma, sweating, miosis, muscular twitching, lacrimation and salivation.
Mycetismus nervosus Ingestion of  mushroom muscarine violent vomiting,  diarrhea, profuse sweating, convulsions, contracted pupils and
Mycetismus sanguinareus ingestion of raw or under cooked false morel mushrooms  monomethyl hydrazine hemoglobinuria and transient jaundice
Mycetismus cerebralis Ingesting species of mushroom of the genus Psilocybe psilocybin hallucinations
Inflammatory Gastroenteritis
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Vibrio cholerae- gram negative curved rod Ingestion with contaminated water or food (shellfish, shrimp, oysters) Enterotoxin (84,000 daltons) ADP-ribosyltranferase activity; ADP -ribosylation of GTP binding protein
inhibits the GTP turnoff reaction and causes a sustained increase in adenylate cyclase activity (increases cAMP).
Cholera; Diarrhea; rice water stools; 
Enterotoxigenic (ETEC) E. coli- gram negative rod Ingestion of comtaminated water or food.
ETEC has multiple pathogenic mechanisms which include at least
2 distinct toxins; a heat-labile toxin (LT) and a heat stable toxin (ST). LT is similar to cholera toxin.  The ST acts by stimulation of guanylate cyclase with resultant cyclic GMP accumulation in mucosal cells.
Traveler's Diarrhea; watery, self-limited diarrhea, vomiting, cramps, nausea, low-grade fever, 1-3 days duration.
Enteropathogenic (EPEC) E. coli also called enteroadherent E. coli- gram negative rod Ingestion of comtaminated water or food. EPEC produces no demonstrable extracellular toxin. Bfp mediates loose attachment to microvillus cells which leads to increases in Ca levels and then rearrangements in actin, Intimin protein needed for intimate contact will human cells and final stages of cell destruction. Infant diarrhea with fever, nausea, vomiting, nonbloody diarrhea
Enteroaggregative (EAggEC) E. coli- gram negative rod Ingestion of comtaminated water or food. Aggregative pattern due to certain thin pili (GVVPQ fimbriae) Developing countries, persistant watery diarrhea with vomiting and dehydration in infants. Can lead to bloody stools
Clostridium difficile- gram positive rod Treatment of a patient with antibiotics eliminates most of the normal flora allowing C. difficile to overgrow. Enterotoxin A (toxin A; chemotactic for neutrophils, cytokine release, hypersecretion of fluid and hemorrhagic necrosis) and Cytotoxin (toxin B; depolymerizes actin) Pseudomembranous colitis, and/or diarrhea
Vibrio parahemolyticus- slightly curved gram negative rod Ingestion of contaminated undercooked or raw seafood diarrhea (most common cause in Japan)
Bacillus anthracis Ingestion of contaminated undercooked or raw meat (very rare)  nausea, anorexia, and fever followed by abdominal pain and bloody stool
Rotavirus fecal-oral contamination winter diarrhea- diarrhea, fever, abdominal pain and vomiting (mostly in infants.)
Noroviruses (Norwalk-like agents) fecal-oral contamination, foodborne, waterborne   fever, abdominal pain, diarrhea, and vomiting (alot of vomiting).
Norwalk Agent- a Calicivirus fecal-oral contamination summer diarrhea- fever, abdominal pain, diarrhea, and vomiting.
Giardia lamblia (intestinalis)- parasite Ingestion of comtaminated water or food. attach to microvilli of small intestine, no known toxin. giardiasis- fatty, foul smelling diarrhea, flatulence (gas).
Cryptosporidium parvum- parasite Ingestion of comtaminated water or food. mild nausea, abdominal cramping and watery diarrhea, severe and persistant in immunocompromised patients.
Cylospora cayetanensis- parasite Ingestion of comtaminated water or food. Oftentimes, on surface of imported fruits. mild nausea, abdominal cramping and watery diarrhea, severe and persistant in immunocompromised patients.
Invasive Gastroenteritis
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Shigella (S. sonnei (most common in U.S.), S. flexneri, S. boydii, S. dysenteriae) Transmitted by the 4-F's; food, fingers, feces, and flies. enterotoxin acts like E. coli LT toxin and cholera toxin.  fever and cramping
abdominal pain are prominent. Diarrhea usually appears after 48 hours, with dysentery supervening about 2
days later.
Salmonella typhi, Salmonella paratyphi A, B, and C, Salmonella cholerasuis  ingestion of fecally contaminated food or water able to survive in neutrophils typhoid fever, paratyphoid or enteric fevers=  anorexia,    lethargy, malaise, general aches, pains,   dull continuous headache usually confined to the frontal regions, nonproductive cough, nosebleed (10% of patients), vague abdominal pain and discomfort, constipation (20% of patients have mild diarrhea), abdominal distension due to gas in the intestines, bloody feces
Salmonella enteriditis (contains 7 subgroups and 1500 serotypes)-gram negative rod Fecal-oral transmission via contaminated water, food
(poultry, eggs, or dairy products), or directly in young children
nausea, vomiting, diarrhea
Campylobacter jejuni-coma or sea gull-shaped gram negative rod animal to human transmission, contaminated water, raw milk and food (especially poultry) Enterotoxin - similar to the LT toxin of Escherichia coli (causes diarrhea) 
Verotoxin - similar to the Shigella toxin (causes hemorrhagic colitis) 
bloody diarrhea
Escherichia coli  Enteroinvasive E. coli (EIEC)- gram negative rod Ingestion of contaminated food and water. Plasmid mediated invasion of epithelial cells fever, cramping, watery diarrhea, followed by scant bloody stools
Escherichia coli Enterohemorrhagic E. coli (EHEC) includes  serotype O157:H7- gram negative rod Ingestion of contaminated food (undercooked hamburgers), and water Verotoxin-blocks protein synthesis bloody diarrhea and in severe cases can lead to hemolytic uremic syndrome (HUS)
Vibrio vulnificus- slightly curved gram negative rod contaminated shellfish Sepsis and targetoid lesions in patients with liver problems
Yersinia enterocolitica and Yersinia pseudotuberculosis- gram negative rod Found in colder areas, e.g., northern USA. Spread via contaminated meat
or milk. 
Invasin allows entry into cells in the Peyer's patches diarrhea, fever, abdominal pain
Francisella tularensis Ingestion of uncooked or undercooked mammals Continuous fever (without chills or sweats), Myalgias (muscle pains), Severe headaches,     Hepatosplenomegaly 
Usually no vomiting or diarrhea.
Helicobacter pylori- curved rod shaped (doesn't stain well by gram stain- gram negative in structure) fecal oral spread

Urease, vacuolating cytotoxin (Vac A), cytotoxin-associated gene A (Cag A). The bacteria produce large amounts of urease allowing them to generate ammonium ions, which buffer the gastric acid. The Vac A protein causes vacuoles to form in certain cells and has been demonstrated to cause pore formation in human cells. The cagA gene product is injected in host cells by the bacteria, which causes several changes in host cell signaling.

Peptic ulcer, Gastritis results in dyspepsia, cramps, halitosis, ructus, nausea, vomiting and flatulence. 
Entamoeba histolytica- parasite Transmitted by the 4-F's; food, fingers, feces, and flies. dysentery= bloody mucoid diarrhea, flask- shaped ulcers in the colon.
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Last revised 6/11/08