Term
| Patient comes in complaining of vomiting, but has no fever or diarrhea. No bacteria are observed in the stool. The patient's last meal was a mayonnaise-laden sandwich from the local deli, which occured 2-4 hours before . What is the most likely etiology/pathology for the patients illness? What are some of the treatment options? |
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Definition
Staph aureus in the mayonnaise deposits heat/acid-resistant enterotoxin. This enterotoxin affects neural receptors of the upper GI tract, stimulating emesis.
The illness is self-limiting, typically within 24 hrs. |
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| Patient comes in after eating at a Chinese restaurant 1-6 hours ago. He mentions the fried rice was somewhat funky tasting, and has been vomting the whole morning, with little diarrhea or fever. What is the most likely pathology for his symptoms? What if he complained of unconrolled diarrhea instead of emesis? |
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Definition
Bacillus cereus typically inhabits starchy foods, such as fried rice. The type 1 endotoxin is the emetic form.
Type 2 B. cereus stimulates adenylate cyclase/cAMP production, leading to diarrhea. |
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| Patient comes in complaining of severe watery diarrhea, with fatigue, but no fever, chills or headache. Blood work-up shows low serum protein and glucose levels. He mentions eating some reheated chicken that tasted weird, but that was 8-14 hours ago. What is the most likely etiology? |
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Definition
Clostridium perfringens enterotoxin. Organism is ingested as a heat-resistant spore. Upon ingestion, the bacteria sporulates, releasing a heat-labile enterotoxin that inhibits glucose transport, damages intestinal epithelium and causes protein loss into intestinal lumen.
Like many other non-inflammatory gastroenteritis intoxications, the symptomatic phase is self-limited to 24 hours. |
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| Patient returns from camping trip with dramatic amounts of watery diarrhea. There is no evidence of inflammation (no leukocytes in stool, fever, etc.) Endoscopic biopsy reveals G- curved rods with flagellum on the surface of the intestine, but none within. What is the most likely etiology and what is the most important treatment? |
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Definition
Vibrio cholerae, releasing toxin (co-regulated with pili). The toxin induces secretory diarrhea vi a adenylate cyclase.
It is important to rehydrate patient with fluids containing electrolyte. If special fluid is not available, add 5g NaCl to 50g of precooked rice cereal or 40g sucrose to 1L of drinking water. |
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Term
| On your visit to Japan, you make the mistake of eating in a questionable sushi restaurant. What bacteria and consequent symptoms should you be on the look-out for? |
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Definition
| Vibrio parahaemolyticus, water diarrhea. |
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Term
| Patient comes straight from JFK, returning from their travels around the world. Patient has severe diarrhea, cramping and blood in their stool. Labs show uremia as well as thrombocytopenia and anemia. What is the most likely diagnosis and etiology? |
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Definition
Enterotoxogenic E. coli (ETEC) is the most common form of travelers diarrhea, leading to diarrhea, dysentery and hemolyic uremic syndrome. It is a strain of E. coli NOT part of the normal flora.
Two toxins have been observed: a heat-labile, Cholera-esque toxin, and a heat-stabile, guanylate cyclase stimulator. |
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Term
| An infant comes in with water diarrhea, accompanied by fever and vomiting. However, no inflammatory signs are observed (e.g. no leukocytes in stool). Intestinal biopsy shows gram- rod adhering tightly to the small intestinal microvilli. What is the most likely pathology? |
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Definition
| Enteropathogenic E. coli (EPEC) adheres and effaces by injecting attachment protein (intimin) along with E.coli secretion proteins (Esps) and intimin receptor into the intestinal membrane. |
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Term
| A patient at the AIDS clinic has diarrhea, vomiting, as well as symptoms suggesting inflammation (fever, leukocytes and blood in stool). Endoscope shows clumping of bacteria and mucus-bacteria biofilm. What's the likely diagnosis? |
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Definition
| Enteroaggregative E. coli (EAggEC). Similar to ETEC. Also seen in infants <6 mohtns. |
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Term
| What is the mechanism and pathology for C difficile infection? |
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Definition
| Endogenous colonic organism that can overgrow due to antibiotic or antineoplastic agent. Releases toxin A (attracts neutrophil, induces release of cytokines, causes hypersecretion and hemorrhagic necrosis). Cytotoxin B de-polymerizes actin, leading to lethal inflammation of colon and pseudomembrane. Consequence is severe diarrhea. |
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Term
| Patient dies after eating uncooked meat. Before death, he complained of pain, fever, vomiting, etc. On autopsy, lymphadenopathy seen in small intestine, as well as general hemorrhagic inflammation. What's the diagnosis? |
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Definition
| Ingested Bacillus anthracis (very rare in humans) |
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Term
| What is the pathology of Shigella infection? |
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Definition
- Shigella invades (requires plasmid-borne antigens, responsible for ulcerative inflammation) M cell from intestinal lumen
- Bacteria escapes vacuole to enter cytoplasm
- Forms actin "rocket" that shoot it into macrophages
- Shigella invades adjacent cells from basolateral side
Additional notes: toxin A-B stops protein synthesis, causing HUS; PMN transmigration facilitates infection by disrupting tight junctions |
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Term
| What is the most common source of diarrhea in the US? What is notable about the bacteria that causes it? |
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Definition
Campylobacter jejuni, an invasive, inflammatory bacteria
- Releases toxins (cytolethal distending toxin) that arrest host cell DNA.
- Cytochrome oxidase positive
- Associated with Guillan-Barre syndrome (believed to be molecular mimicry directed again peripheral nerves)
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Term
| Patient comes in after eating a hamburger at Jack-in-the-Box. You see an attaching-effacing lesion on endoscope, but capillary thrombosis and colonic inflamation as well. What's the nost likely diagnosis? |
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Definition
Enterohemorrhagic E. coli (EHEC)
While the lesions are similar to EPEC, the Shiga-like toxin induces bloody diarrhea, hemorrhagic colitis and HUS. Cattle resevoir in Western nations (hamburgers) |
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Term
| What is the breakdown for Salmonella subspecies? |
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Definition
- Those that cause gastroenteritis (S. tymphimurum, enteridis and cholerae-suis).
- Those that cause enteric fever (S. typhi)
- Those that cause bacteremia (S. cholerae-suis)
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Term
| What are the mechanisms of host resistance in the saliva? |
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Definition
- Salivary glycoproteins bind to bacteria cell receptors and prevent attachment
- IgA, IgM and IgG release
- Lactoferrin sequesters iron (kills Vibrio, Pseudomonas, E. coli)
- Lysozyme targets G+
Radiation can lead to xerostomia --> GI oral infection
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