Molecular characterisation and pathogenicity evaluation of Aeromonas hydrophila strains isolated from cultured tilapia Oreochromis niloticus in Egypt

Abstract

The objectives of the present study were to  characterise Aeromonas hydrophila isolated from diseased tilapia Oreochromis niloticus  cultured in Kafrelsheikh farms and to  evaluate virulence and pathogenecity. About 200 adult fish exhibiting the onset of clinical signs were bacteriologically examined using Aeromonas isolation medium. The isolates were identified by 16S rRNA gene sequence analysis using species specific primers and then tested for ten virulence genes employing specific primers. Experimental challenge studies were also conducted to investigate the pathogenicity of the recovered A. hydrophila strains. Thirty five isolates were identified as A. hydrophila based on 16S rRNA gene sequence analysis, which were also positive for presence of four virulence genes (aerolysin, lipase, cytotonic heat stable enterotoxin and haemolysin). Results showed that majority of the examined strains carried one or more virulence genes.

Keywords: Aeromonas hydrophila, Molecular techniques, Oreochromis niloticus, Virulence genes