Reductions of Vibrio parahaemolyticus in oysters after bacteriophage application during depuration

Vibrio parahaemolyticus is closely associated with oysters in China, which are normally consumed raw or lightly cooked. Bacteriophages are a safe bio-controlling agent, and have been recognized in aquaculture for their pathogen reduction properties. This study investigated the potential application of the bacteriophage VPp1 during depuration to reduce V. parahaemolyticus in oysters at different multiplicity of infection (MOI) and temperature levels. Oysters were infected with 105, 106, and 107 colony-forming units (CFU)/mL of V. parahaemolyticus in the seawater and each infected group was treated with three different MOI values: 10, 1, and 0.1. Infected oysters were depurated in non-recirculating seawater at 22 °C, 20 °C, 16 °C, and 12 °C for 36 h. Results revealed that temperatures < 20 °C were safe for oyster rearing. Depuration at 16 °C with 0.1 MOI was the best condition for reducing V. parahaemolyticus in oysters, which decreased by 2.35-2.76 log CFU/g within 36 h. This study provides the basis for the use of bacteriophages in depuration techniques to eliminate V. parahaemolyticus in oysters.