A patient develops severe watery diarrhea after consuming contaminated seafood. Stool culture grows a Gram-negative, comma-shaped bacterium that produces a toxin causing irreversible activation of adenylyl cyclase. Which organism is the most likely culprit?

The correct answer to the question "A patient develops severe watery diarrhea after consuming contaminated seafood. Stool culture grows a Gram-negative, comma-shaped bacterium that produces a toxin causing irreversible activation of adenylyl cyclase. Which organism is the most likely culprit?" is Option C: Vibrio cholerae.

The other options — A) Salmonella typhi, B) Shigella dysenteriae, D) Escherichia coli O157:H7 — are incorrect for this USMLE Exam Prep question. As explained above: Vibrio cholerae produces cholera toxin, which ADP-ribosylates the Gs alpha subunit, leading to irreversible activation of adenylyl cyclase and increased cAMP. This causes massive secretion of water a…