Pathogenicity of Vibrio alginolyticusfor Cultured Gilt-Head Sea Bream (Sparus aurataL.)

Abstract

ABSTRACTThe in vivo and in vitro pathogenic activities of whole cells and extracellular products ofVibrio alginolyticusfor cultured gilt-head sea bream were evaluated. The 50% lethal doses ranged from 5.4 × 104to 1.0 × 106CFU/g of body weight. The strains examined had the ability to adhere to skin, gill, and intestinal mucus of sea bream and to cultured cells of a chinook salmon embryo cell line. In addition, the in vitro ability ofV. alginolyticusto adhere to mucus and skin cells of sea bream was demonstrated by scanning electron microscopy. The biological activities of extracellular products ofV. alginolyticuswere hydrolytic activities; the products were able to degrade sea bream mucus.V. alginolyticuswas cytotoxic for fish cell lines and lethal for sea bream. Moreover, the extracellular products could degrade sea bream tissues. However, experiments performed with the bath immersion inoculation technique demonstrated thatV. alginolyticusshould be considered a pathogen for sea bream only when the mucus layer is removed and the skin is damaged.