Effect of temperature on uptake and survival of Vibrio parahaemolyticus in oysters ( Crassostrea plicatula)

Abstract

This study investigated accumulation of Vibrio parahaemolyticus in Zhe oyster ( Crassostrea plicatula) from culture water and effectiveness of frozen and chilled storage on reducing V. parahaemolyticus in oysters. Freshly harvested oysters were placed in artificial seawater containing V. parahaemolyticus (10 4 CFU/mL) at 16, 20, 26, and 32 °C for 96 h. Contaminated oysters were stored at chilled temperatures (0, 5, and 15 °C) and frozen at − 18 and − 30 °C and changes of V. parahaemolyticus populations in oysters were determined using the most probable number (MPN) method. Accumulations of V. parahaemolyticus in C. plicatula reached the peaks at 6.66 (32 °C), 5.72 (26 °C), 5.04 (20 °C), 4.72 (16 °C) log MPN/g after 32 h in contaminated artificial seawater. Holding contaminated Zhe oysters at 5 and 0 °C reduced V. parahaemolyticus populations in both shell stock and shucked oysters. Populations of V. parahaemolyticus in shell stock and shucked oysters declined by 1.42 and 2.0 log MPN/g, respectively, after 96 h of storage at 5 ºC and by 2.11 and 2.38 log MPN/g, respectively, after 96 h of storage at 0 °C. However, populations of V. parahaemolyticus increased by 2.44 log MPN/g in shell stock oysters and by 1.64 log MPN/g in shucked oysters when stored at 15 °C for 60 h. Frozen storage was effective in inactivating V. parahaemolyticus. Populations of V. parahaemolyticus in shell stock and shucked oysters decreased from 5.46 log MPN/g to 1.66 and 0.38 log MPN/g, respectively, after 75 days of storage at − 30 °C. No V. parahaemolyticus cells were detected (<3 log MPN/g) in the shucked oysters after 60 days of storage at − 18 °C. These results demonstrated that accumulation of V. parahaemolyticus in cultured C. plicatula increases as water temperature increases. Harvested C. plicatula should be stored at 5 °C or lower to control the hazard of V. parahaemolyticus.