Screening of marine lactic acid bacteria for Vibrio parahaemolyticus inhibition and application to depuration in Pacific oysters (Crassostrea gigas).

Abstract

This study aims to assess the use of marine lactic acid bacteria (LAB) to reduce V. parahaemolyticus levels during oyster depuration process. The inhibitory effect of thirty marine LAB strains against V. parahaemolyticus strains was evaluated by in vitro assays. Three positive strains (Latilactobacillus sakei SF1583, Lactococcus lactis SF1945 and Vagococcus fluvialis CD264) were selected for V. parahaemolyticus levels reduction during oyster depuration. Pacific oysters Crassostrea gigas were artificially and independently contaminated by four GFP-labelled V. parahaemolyticus strains (IFVp201, IFVp69, IFVp195 and LMG2850T) at 105 CFU.mL-1 and then exposed by balneation to 106 CFU.mL-1 of each LAB strains during 24h, at 19°C. Quantification of V. parahaemolyticus in haemolymph by flow cytometry revealed variations in natural depuration of the different V. parahaemolyticus strains alone. Furthermore, the addition of LABs improved up to 1-log bacteria.mL-1 the reduction of IFVp201 concentration in comparison to the control condition. Although further optimizations of procedure are needed, addition of marine LABs during oyster depuration may be an interesting strategy to reduce V. parahaemolyticus levels in C. gigas. Our study provides promising ways to develop a depuration process which could potentially be implemented in oyster farms.