A man develops diarrhea and fever, and a stool culture shows a gram-negative rod that does not ferment lactose and does not produce hydrogen sulfide. Which organism is the most likely?
Answer and explanation
Correct answer: A. Shigella
- Step 1: Shigella is a non-lactose-fermenting, H2S-negative, nonmotile rod. Step 2. It causes bloody dysentery with a very small infectious dose. Answer: Shigella. Why not the others: Salmonella produces hydrogen sulfide, E. coli ferments lactose and Vibrio causes watery diarrhea.
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