Bacteriological and molecular assay of Vibrio species affecting some marine and freshwater fishes

Aquatic animals are susceptible to a serious disease called vibriosis that causes high mortality rates, financial losses, and foodborne outbreaks. So, the present study was planned to isolate and identify the prevalence of Vibrio species in some freshwater and marine water fishes at Kafer El-Sheikh governorate, Egypt. A total of 200 fish samples, 100 freshwater fish [Nile tilapia (Oreochromis niloticus)], 100 marine fish [20 Red porgies (Pagrus pagrus), 30 Gilthead seabream (Sparus aurata), and 50 European seabass (Dicentrarchus labrax)] were subjected to clinical, bacteriological and molecular diagnosis for Vibrio infection. Clinical observations revealed diseased fish included dark skin, redness, detached scales, fin erosion, and irregular hemorrhagic patches. Bacteriological identification showed that the isolation rate of Vibrio in Nile tilapia was (23%) compared to (34%) in marine fish (15%, 17%, and 52% from red porgy, Gilthead seabream, and European seabass, respectively), where the highest percentage encountered in European seabass. Among Nile tilapia isolates, Vibrio alginolyticus was the most detected species (52%) followed by Vibrio parahaemolyticus (39%) then Vibrio cholera (9%). Meanwhile isolation from marine fish showed (50%), (41%) and (9%) for Vibrio parahaemolyticus, Vibrio alginolyticus and Vibrio harveyi respectively. Moreover, the molecular identification of the isolates by PCR confirmed the identity of the Vibrio parahaemolyticus, Vibrio alginolyticus and Vibrio cholera through the presence of the species specific genes (transmembrane regulatory protein, toxR gene), (collagenase gene) and (Superoxide dismutase B, sodB gene), respectively. These results indicate the high rate of Vibrio infection in marine and freshwater fishes at Kafer El-Sheikh Governorate,Egypt.