Role of extracellular products in the pathogenicity of Vibrio strains on cultured gilt-head seabream (Sparus aurata).

The enzymatic activities of extracellular products (ECP) from different pathogenic Vibrio strains and their virulence for fish (cultured gilt-head seabream, Sparus aurata L.) were tested. ECP were obtained by growing the bacteria on cellophane overlays. Cytotoxic effects of ECP on fish cell lines were rapid and strong, provoking mortality of fish after 24 to 72 h of the ECP inoculation. A close relationship between proteolytic activities (gelatinase and caseinase) of the ECP and the presence of lytic effects in the muscular tissue at the injection site was observed. Therefore, these activities may be considered responsible for the fish tissue damage.