Abstract
Marine fish plays an important role in the human diet with an observed increase in the consumption of marine fish. Thus, it is necessary to study the prevalence of pathogens in fish to ensure the safety of fish and fish products. A total of 100 random samples of marine water fish represented by Sardine (Sardina pilchardus), Barbone (Mullus surmuletus), Saurida undosquamis (Mackerel) and Sparus aurata (Denise) (25 of each) were collected from local markets in Alexandria Governorate. Samples were examined bacteriologically immediately after arrival to the laboratory for isolation and identification of Salmonella, Yersinia and Vibrio species. The obtained results revealed that incidence of Salmonella isolated from the examined samples of marine fish species was 16, 8, 4 and 8% in Sardine, Barboni, Mackerel and Dinese, respectively. Serotyping of Salmonella isolated from the examined samples of marine fish clarified the detection of S. Enteritidis, S. Typhimurium and S. Haifa. Also, it was found that the incidence of Yersinia isolated from the examined samples of marine fish species was 44, 36, 24 and 28 % in Sardine, Barboni, Mackerel and Dinese, respectively and the biochemical identification clarified the detection of Y. enterocolitica, Y. frederiksenii, Y. ruckeri and Y. intermedia. Finally, the incidence of Vibrio isolated from the examined samples of marine fish species was 36, 24, 20 and 16 % in Sardine, Barboni, Mackerel and Dinese, respectively and the biochemical identification of the obtained isolates of Vibrio clarified the presence of V. parahaemolyticus and V. cholera. On the basis of the previously mentioned results, Salmonella, Yersinia and Vibrio still constitute common contaminants of marine fish and its presence is very important due to its public health significance, good hygienic measures must be applied to obtain safe marine fish.

Key words: Salmonella, Yersinia, Vibrio, Isolation, Marine water fish