Question

Which of the following organism releases histamine and cause scombroid fish poisoning

• A. Salmonella
• B. Staphylococcus
• C. P. aeruginosa
• D. Weissella

Answer 1

The Correct Option is C

Step 1: Reframe the disease: scombroid is essentially histamine toxicity, not an infection. Spoiled, warm-stored scombroid fish accumulate histamine when bacteria convert the amino acid histidine. Step 2: The bacteria that carry $histidine\ decarboxylase$ are surface and gut gram-negative enterics of the fish - the textbook example is Morganella morganii, with Pseudomonas aeruginosa, E. coli and Klebsiella also implicated. Step 3: Scan the choices for any of those: Salmonella (no), Staphylococcus (no, gram-positive), Weissella (no), Pseudomonas aeruginosa (yes). Step 4: The only matching histamine-producing gram-negative listed wins. \[\boxed{\text{P. aeruginosa}}\]