USMLE Step 1 Question 386

Question:

A 4-year-old girl came home from day care and developed fever, abdominal pain, and diarrhea containing flecks of bright-red blood and pus. The girl did not ingest any food at day care. Which is the most likely causative organism?

Correct Answer: E.  Yersinia enterocolitica

Yersinia enterocolitica (choice E) occurs most often in young children, especially at day-care centers.
Common symptoms include fever, abdominal pain, and diarrhea, which is often bloody. Symptoms typically develop 4 to 7 days after exposure and may last 1 to 3 weeks or longer.

Shigella dysenteriae (choice C) is a non-motile gram-negative rod. Humans are the only hosts for Shigella, and it usually causes bloody diarrhea.

Enterotoxigenic Escherichia coli (choice A) and Vibrio cholera (choice D) are both gram-negative rods that cause watery diarrhea.

Campylobacter jejuni (choice B) causes bloody diarrhea, but is usually due to ingestion of contaminated foods or water, with animals as the main reservoir. There is no given history of possibly contaminated food ingestion.