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The in vivo and in vitro pathogenic actions of whole cells and extracellular products of Vibrio alginolyticus for cultured gilt-head sea bream were studied. The strains were able to fasten to the skin, gills and intestinal mucus of sea bream and to cultured cells of a chinook salmon embryo cell line. The extracellular products were observed to destroy sea bream mucus and tissues. V. alginolyticus was cytotoxic for fish cell lines and deadly for sea bream.

The adhesive kinetics of Vibrio strains isolated from diseased gil-head sea bream to superficial skin mucus was investigated by adhesive assay and spectroscopy. Data indicated saturation kinetics for V. anguillarum-like strains, whereas V. alginolyticus showed a proportional adsorption kinetics. Mucus did not have an effect on the adhesive ability of the pathogenic microorganisms, suggesting that there is no relationship between adhesive capability for skin mucus and virulence.

Research was conducted to examine the chemotaxis of pathogenic Vibrio strains towards mucus surfaces of gilt-head sea bream Sparus aurata L and to stuy the influence of salinity and temperature on the process. Twenty-two strains of Vibrio anguillarum and Vibrio alginolyticus were isolated from diseased gilt-head sea bream and their abilities to assay were determined following the preparation of raw skin, gill and intestinal mucus. Results indicate that the mucus surfaces are potential portal entries in the fish for V anguillarum and V alginolyticus.