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A 20-year-old man without a significant past medical history comes to the clinic complaining of severe vomiting for the last 10 hours. He denies fevers and reports only 1 episode of small volume, non-bloody diarrhea. He lacks significant abdominal pain. The symptoms reportedly began 6 hours after eating a hamburger and macaroni salad at a neighborhood fast food restaurant. His temperature is 37 C (98.6 F), blood pressure is 105/70 mm Hg, pulse is 100/min, and his respirations are 17/min. He has slightly dry mucous membranes, a non-tender abdomen with decreased bowel sounds, and guaiac-negative stool. The most likely etiology of his gastrointestinal complaints is
A. Bacillus cereus
B. Campylobacter jejuni
C. Clostridium perfringens
D. E. Coli (0157:H7)
E. Staphylococcus aureus
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E Staph aureus (C perfringens would have had prominent abdominal cramps)
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E - preformed exotoxin from s aureus
b. cereus - reheated rice
EHEC - would've presented with excessive bloody stool
C perfringens - cramping due to CO2 production and from reheated meat
campylobacter - bloody diarrhea
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yup all u are right
The correct answer is E. This patient has an illness which is caused by a preformed toxin. S. aureus is a likely culprit in this patient. Staphylococcus produces a preformed toxin, which is obtained from dairy products such as mayonnaise. The illness that follows typically occurs 1-8 hours after ingestion of the toxin. Fever is usually absent and vomiting is major feature of these illnesses. Diarrhea can occur but to a lesser extent than the vomiting. The illness is self limiting and will resolve in 24-48 hours. Treatment involves electrolyte and fluid resuscitation. Antibiotics are not indicated.
Bacillus cereus(choice A) presents in a similar fashion to S. aureus toxin. There is a short incubation period followed by vomiting with a lack of fever. Treatment is identical. The two are differentiated by the types of foods that they are associated with. Bacillus Cereus is typically associated with reheated Chinese fried rice.
Campylobacter jejuni (choice B) causes bloody diarrhea and fevers. Flouroquinolones are indicated in severe cases.
Clostridium perfringes (choice C) causes another toxin based "food poisoning" illness but with different features. This organism is ingested and then produces its toxin while in the gut, thereby causing a longer latent period of 8-16 hours before symptoms begin. Symptoms typically include more abdominal cramping and diarrhea than S. aureus and Bacillus cereus . Treatment is again supportive with resolution in 1-4 days.
Fast food restaurant questions on the USMLE should always make you think about E. Coli 0157:H7 (choice D). This is a strain of E. coli obtained by eating undercooked hamburger meat. There is typically a latent period between 24-72 hours followed by a severe hemorrhagic colitis with fevers and abdominal pain. This patient's symptoms are not consistent with this organism
