Formation of histamine by luminous bacteria isolated from scombroid fish

The present work was carried out to investigate the role of luminous bacteria particularly Photobacterium sp. in relation to histamine formation when scombroid fish were stored at low temperatures. The numbers of luminous bacteria on the skin of mackerel and herring did not increase during storage in ice but in the viscera they increased greatly during storage in ice and at 10°C. Moreover, the percentages of luminous bacterial counts (LBC) comprised 20% or more of the flora (TVC) during storage in ice and at 10°C as compared with 0.4% in fresh fish. Eighty-five out of 90 strains of the luminous bacteria isolated were identified as Photobacterium phosphoreum and 5 strains of the isolates as Vibrio logei. All the strains of P. phosphoreum isolated formed histamine with high levels in some strains but V. logei and fish spoilage bacteria comprising certain strains of Pseudomonas putida, Pseudo-monas Gp III and Moraxella sp. did not. From these findings, it is considered that P. phosphoreum may play a significant role in hista-mine formation when scombroid fish are stored at or below temperatures of 10°C.