Bacterial pathogens causing mortalities in the sea bass (Dicentrarchus labrax) and determination of seasonal occurrence in the Eastern Black Sea

In Black Sea, bacterial sampling of kidney and spleen of 476 sea bass (Dicentrarchus labrax) carried out monthly, from June and December, from Perşembe and Yomra growout farms. The first gill arc of each sampled fish was also sampled to determine the number of gill parasite of the isolated 137 bacteria were characterized biochemically tests, including antibiogram profiles. Besides their family and species were identifed by the help of 16s rDNA sequence analysis. Of the isolated 24 bacteria species , the most frequently isolated bacteria that are pathogenic to fish were Aeromonas veronii (47,6%), Photobacterium damselae subsp. damselae (14%), Vibrio vulnificus (5%), Vibrio rotiferianus (3,3%) and Vibrio harveyi (3,3%). Twelve cases of mix infections involving up to three bacteria and gill parasite, were also detected. Moreover Listonella anguillarum, Vibrio ponticus, Vibrio furnissii and Vibrio parahaemolyticus were the other pathogenic bacteria rarely detected. Diplectanum aequans was the only parasite with high prevelans (up to %92). It is observed that the more the numbers of the bacteria increases, the more possiblity of isolation of the bacteria increases. In our study surprisingly zoononic pathogens (Bacillus thuringiensis, Bacillus anthracis strain Ames, Staphylococcus haemolyticus) and Bacillus safensis FO-036b were frequently isolated indicating that farms were under the influence of domestic and agricultural effluents. These isolated bacterial fish pathogens characterised in this study were the first detected and report in this study for the region.