Bacterial production of histamine in some tropical fish

Quantitative and qualitative distribution of histamine-forming bacteria associated with the fish Rastrelliger kanagurta, Sardinella longiceps, Sillago sihama and Liza subviridis, were investigated. These bacteria constituted a significant portion of the total bacterial population of fish and the values obtained in the present study were higher than those previously reported. The order of quantitative abundance of histamine-forming bacteria in the fish examined was: S. longiceps greater than R. kanagurta greater than S. sihama greater than L. subviridis. The bacterial genera isolated were Vibrio sp., Bacillus sp., Pseudomonas sp., Aeromonas sp. and Micrococcus sp., and among them Vibrio was dominant. Growth of the isolates (Vibrio sp., V. fischeri and Bacillus sp.) at different temperatures, pH and sodium chloride concentrations indicated them to be mesophilic, euryhaline and tolerant to acidic and alkaline pH. Bacillus sp. produced more histamine in R. kanagurta, while V. fisheri produced more histamine in S. longiceps.