Effects of "host factor" bile on adaptability and virulence of Vibrios, foodborne potential pathogenic agents

In order to improve the knowledge of host/pathogenic agent interaction and to obtain a more careful estimation of risk related to ingestion of food contaminated by Vibrio spp., the effects of bile extracts have been studied. The growth of one V. fluvialis, two V. alginolyticus, and three V. parahaemolyticus strains, isolated from mollusks and crustaceans, has been determined to evaluate their adaptability to intestinal environment. Moreover, the expression of virulence factors responsible for the colonization, as bacterial "swarming mobility", biofilm production, adherence on epithelial cells and hydrophobicity, has been evaluated. Using a bile concentration of 1.5%, all examined strains showed a constant inhibitory effect, quite moderate in the first growth phases. Bile increased the "swarming mobility" and biofilm production; also the adherence was favored, but only after adaptation and during the early logarithmic phase. The decreased hydrophobicity could explain the reduction of adherence during the stationary phase. Studying the phenotypic expression of virulence factors in "minor vibrios" in the presence of bile, it was possible to extend the knowledge about their pathogenetic mechanisms owing to the ingestion of contaminated food. That permits a more careful estimation of risk related to the contamination, considering the high frequency of isolation of these species in some seafood.