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

Abstract

Aims: This study aims to assess the use of marine lactic acid bacteria (LAB) to reduce Vibrio parahaemolyticus levels during oyster depuration process.

Methods and results: The inhibitory effect of 30 marine LAB strains against V. parahaemolyticus strains was evaluated by in vitro assays. A total of 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 24 h, 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.

Conclusions: 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 Crassostrea gigas.

Keywords: V. parahaemolyticus; challenge test; flow cytometry; lactic acid bacteria; oyster depuration; seafood safety.