PATHOGENICITY OF VIBRIO-ALGINOLYTICUS FOR CULTURED GILT-HEAD SEA BREAM (SPARUS-AURATA L.)

The in vivo and in vitro pathogenic activities of whole cells and extr acellular products of Vibrio alginolyticus for cultured gilt-head sea bream were evaluated. The 50% lethal doses ranged from 5.4 x 10(4) to 1.0 x 10(6) CFU/g of body weight. The strains examined had the ability to adhere to skin, gill, and intestinal mucus of sea bream and to cul tured cells of a chinook salmon embryo cell line, In addition, the in vitro ability of V. alginolyticus to adhere to mucus and skin cells of sea bream was demonstrated by scanning electron microscopy. The biolo gical activities of extracellular products of V. alginolyticus were hy drolytic activities; the products were able to degrade sea bream mucus . V. alginolyticus was cytotoxic for fish cell lines and lethal for se a bream. Moreover, the extracellular products could degrade sea bream tissues, However, experiments performed,vith the bath immersion inocul ation technique demonstrated that V. alginolyticus should be considere d a pathogen for sea bream only when the mucus layer is removed and th e skin is damaged.