Enhancing bivalve depuration using a phage cocktail: An in vitro and in vivo study

Bivalves are increasingly valued in the global diet; however, as filter feeders, they can accumulate pathogenic bacteria, posing infection risks to consumers. Although depuration is the standard process for reducing microbial loads in bivalves, it is often less effective against resilient pathogens such as Vibrio spp. Bacteriophage biocontrol offers a promising, eco-friendly alternative for managing bacterial contamination. This study evaluated a cocktail of five phages—PCEc3, PCST1, PCSE1, PCAh2, and PCVp3— targeting five major bacteria of concern associated with shellfish consumption: Escherichia coli, Salmonella enterica serovars Typhimurium and Enteritidis , Aeromonas hydrophila, and Vibrio parahaemolyticus . The phage cocktail reduced in vitro bacterial loads for each bacterium by 3.76–4.99 log CFU/mL within 10 h and 3.57 log CFU/mL in the bacterial mixture within 8 h. All phage titres remained stable under salinity, pH, and temperature conditions typical of industrial depuration, with minimal reductions observed after 7 days. In artificially contaminated cockles ( Cerastoderma edule ), the phage cocktail reduced the bacterial load by 0.85 log CFU/g after 6 h in a recirculating industrial depuration system without affecting cockle survival. However, its efficacy in vivo was lower than observed in vitro . Optimisation strategies, such as applying phages before depuration or combining static and recirculating techniques, could enhance effectiveness in industrial settings. Overall, combining phage biocontrol with depuration procedures offers a promising approach to improving the quality and safety of depurated bivalves for human consumption. • Phage cocktail inactivates pathogens associated with bivalve consumption in vitro. • Phages titres remained stable under depuration-related conditions. • Phage cocktail enhances bacterial clearance in bivalves during depuration. • Phage biocontrol does not affect bivalve survival during depuration.