Abstract

This study characterises the Aeromonas and Vibrio strains isolated from seawater and sediments out of Sparus aurata marine farm. The bacterial strains were isolated on Thiosulfate-Citrate-Bile-Sucrose (TCBS) agar plates and described using different bacteriological tests and using standardised micro-methods “API 20 NE strips”. The exoenzymes production and antibiotics susceptibility were also investigated. Theenterobacterial repetitive intergenic consensus (ERIC)-PCR was used to evaluate the genetic diversity of the isolated strains. Two dominant genera of bacteria were found (Aeromonas and Vibrio). Aeromonas hydrophila strains were the dominant bacteria (56.5% of total isolates) followed by V. alginolyticus strains (26.1%). Most of the studied strains were β-haemolytic, hydrolyze the DNA and produce many exoenzymes such as lecithinase, caseinase, amylase and lipase. All tested strains were resistant to at least three antimicrobial agents. The antibiotic resistance index was 0.683 for V. alginolyticusand 0.711 for A. hydrophila strains. The ERIC-PCR profiles among the isolated bacteriawere generally heterogeneous, showing a high polymorphism between Aeromonasstrains.

Key words: Aeromonas spp., Vibrio spp., seawater, genetic diversity, virulence properties.