Viability and Histidine Decarboxylase Activity of Halophilic Histamine-Forming Bacteria During Frozen Storage.

The specific activity of histidine-decarboxylase of halophilic histamine-forming bacteria, Photobacterium phosphoreum and Photobacterium histaminum sp. nov., remained 27~53% of the initial value after seven days storage at -20°C, while the viable cells decreased by more than 6 log cycles of the initial counts. This finding suggests the possibility that outbreaks of scombroid fish poisoning are caused by the ingestion of frozen-thawed fish and its products, even when the viable count of histamine-forming bacteria is low.