Question

Histamine producing bacteria in iced fish is

• A. Photobacterium
• B. Staphylococcus
• C. Salmonella
• D. Shewanella

Hint:

Histamine is heat-stable; once it is formed in the fish due to temperature abuse, it cannot be removed by cooking, canning, or freezing. Rapid chilling to 0$^\circ$C immediately after harvest is the only way to prevent its formation.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Histamine poisoning (Scombroid poisoning) occurs when certain fish (like Tuna, Mackerel, Mahimahi) are stored at improper temperatures. Certain bacteria possess the enzyme histidine decarboxylase, which converts the amino acid histidine (found in high amounts in these fish) into toxic histamine. While most histamine-forming bacteria are mesophilic (prefer warmth), some can operate in cold conditions.
Detailed Explanation:
Most well-known histamine producers like Morganella morganii and Klebsiella are inhibited by cold temperatures (icing). However, research has identified "psychrotolerant" (cold-tolerant) histamine producers that can function even when fish is stored in ice.

1. {Photobacterium: Specifically Photobacterium phosphoreum and Photobacterium damselae have been identified as potent histamine producers in vacuum-packed or iced fish. These bacteria are indigenous to the marine environment and can produce significant amounts of histamine even at temperatures as low as 0--5$^\circ$C.
2. {Staphylococcus: Some species can produce histamine, but they are typically mesophilic and associated with poor hygiene, not cold-stored fish.
3. {Salmonella: This is a common enteric pathogen but is not known for significant histamine production in fish.
4. {Shewanella: While Shewanella is a major spoilage bacterium in iced fish (producing $H_2S$ and fishy odors), it is not the primary bacterium targeted for histamine production in cold storage compared to Photobacterium.

Step 2: Final Answer:
Photobacterium is the significant histamine-producing genus that remains active in iced fish.