A new type of histamine-forming bacteria - II. Occurrence of psychrophilic and halophilic histamine-forming bacteria (N-group bacteria) on/in red meat fish.

In a previous paper, the authors reported that psychrophilic and halophilic histamine-forming bacteria, which could produce histamine at 5°C, could be isolated from the common mackerel flesh homogenates stored at 5°C and 20°C, these organisms were named “ N-group bacteria ” for the time being. The present study was undertaken to obtain further information as to the occurrence of Ngroup bacteria on/in red meat fist, common mackerel, saury pike, and sardines. These fish samples were allowed to stand at 2.5°C. N-group bacteria occurred on/in all samples; the number of them in the fresh ones were 1 to 102 per gram of the flesh (0.01 to 1% of total bacterial number), while those in the spoiled ones were 106 to 108 (1 to 10%). N-group bacteria seem to occur as a part of the normal surface microflora of marine fish.