A B S T R A C T

Edwardsiella tarda is one of the serious pathogenic bacteria, infected both cultured and wild fishes species. and has many virulence factors that enhance pathogenesis of bacterial in fishes and cause severe economic losses in aquaculture industry so This study was aimed to isolated Edwardsiella tarda from 150 diseased fish samples ,(60 Nile tilapia (Oreochromis niloticus) ,60 cat fish (Claris gariepinus) , 30 (Mullet (Mugil cephalus) (bayad). from internal organs after clinical and postmortem examination The results revealed that, about 24 isolates of Edwardsiella tarda 12(20%);7 (11.67%) and 5 (16.66%) were isolated from C. gariepinus ,O. niloticus, and M. cephalus fishes respectively. 8 strains formed strong formation biofilm (black colonies ) on cong red agar , 11 moderate(pink ) and 6 negative (white colonies ) 8 out 24 showed resistance to five antibacterial sensitive (oxacillin , ampicillin , sulphamethoprime , gentamycin and Norofloxacin and. Positive results in the amplification of virulence-related genes associated with the pathogenicity of the Edwardsiella tarda in the 8 resistance isolate are positive for production of chondroitinase enzyme gene (cds1), Nacylhomoserine lactones (AHLs)( edwI )gene, vibrioferringene (pvsA) gene and sensor protein implicated gene (qseC) The sequences obtained for ) (qseC) and ( edwI ) genes had accession number MW362141 and MW362142at GenBankand were identical to the corresponding GenBank sequences.which isolated from different sources and countries with no significant differences depending strains host or its area of isolation