MOLECULAR IDENTIFICATION OF Aeromonas hydrophila STRAINS RECOVERED FROM KAFRELSHEIKH FISH FARMS

Abstract

The aim of this study was to recover Aeromonas hydrophila from Kafrelsheikh tilapia (Oreochromis niloticus) farms and to study its virulence. Adult fish (n = 100) exhibiting the onset of clinical signs were bacteriologically examined using aeromonas isolation base medium. The isolates were identified by PCR using A. hydrophila-specific 16S rRNA primers and the virulence was determined using specific primers for ten virulence genes targeting hidrolipase (Lip), elastase (ahyB), lipase (pla/lip), aerolysin (aer), cytotonic enterotoxin (alt), cytotoxic enterotoxin (act), temperature sensitive protease (eprCAI), serine protease (Ahp), haemolysin (hlyA), and cytotonic heat stable enterotoxin (ast). Molecular screening revealed presence of 35 isolates positive for A. hydrophila-specific 16S rRNA and 4 virulence genes (aer, pla/lip, ast, and hlyA). It also showed that the majority of the examined strains carried one or more virulence genes. These data indicate higher virulence for A. hydrophila in infected O. niloticus in Kafrelsheikh fish farms. Key words: PCR; A. hydrophila; virulence genes