Edwardesiellosis in fresh water fish with special reference for detection of some virulence genes by PCR

This study was performed forisolation of Edwardesiella spp. From fresh water fish and molecular identification of some virulence genesas the etiological agent of edwardsiellosis in many fish species. 50 Oreochromis niloticus and 50 Clarias gariepinus, were collected live from fish farms and markets respectively, in Kafrelsheikh Governorate, Egypt. Isolates obtained from the internal organs of examined fish subjected to bacteriological and biochemical identification. Some suspected isolates were confirmed by conventional PCR and three virulence genes highly associated with the pathogenicity of the isolates were identified. A total 21 isolateswere identified phenotypically as E. tarda from both fish species with the higher isolation rate from O.niloticus than C. gariepinus. Eight isolates were identified genotypically by fimA gene and were detected as three Edwardesiella species (37.5%) and these three isolates were confirmed as E. tarda by using gyrB1 gene (100%). Regarding virulence genes, cds1 was indicated in one out of the three isolates (33,3%), pvsA was in two isolates (66,7%) and edwI was absent (zero %) in the three isolates. In conclusion, Presence of these genes render E. tarda highly pathogenic so rapid control was required and fish handlers should take care to avoid infection as it has public health hazard.