Histamine producing bacteria on three fish spices

The objective of this research was to identify the Gram negative histamine producing bacteria, responsible for scombroid intoxication in three fish species: armadillo (Hipostomus watwata), bocachico (Pochilodus reticulates) and lisa (Mugil curema). All of these are highly commercial fish in Venezuela. Thirty six samples were taken and pH was measured, following the Kelleger et al. methodology. Aerobic mesophilic bacteria (RTA) were also determined using American Public Health Association (APHA) criteria. All strains were cultured in Mc. Conkey (MC) and eosin-methylene blue media (EMB), for specific Gram negative isolation. To identify Gram negative histamine producing bacteria, Niven's modified media by Yoshinaga et al. was used, as well as Zinsser's tables for primary and secondary biochemistry. Results showed similar values for pH in all species studied (6.40-6.66). Armadillo RTA was higher than values recommended by ICMSF (10(5)-10(7)). Histamine producing genera were: Escherichia coli, Aeromonas sp, Enterobacter, Citrobacter and Plesiomona shigelloides. A common pattern was observed in armadillo and bocachico in histamine production by: E. coli, and similar patterns were also observed in lisa and bocachico for Aeromonas. The conclusion of this work is that Histamine producing bacteria in armadillo, bocachico and lisa are Escherichia, Aeromonas, Enterobacter, Citrobacter and Plesiomona, similar to those reported in other fish species.