Impact of Feeding Status on the Efficacy of Depuration for Decontaminating Vibrio parahaemolyticus in Pacific Oysters (Crassostrea gigas)

Vibrio parahaemolyticus causes acute human gastroenteritis and is often linked to consumption of raw oysters. Previous investigations indicated that refrigerated seawater depuration at 12.5 degrees C could significantly reduce V. parahaemolyticus contamination in Pacific oysters; however, further optimization is necessary to achieve the regulatory target of >3.52 log most probable number (MPN)/g reduction. The current study investigated influences of algal feeding on efficacy of depuration to reduce V. parahaemolyticus in raw oysters. A V. parahaemolyticus cocktail (10290, 10292, 10293, BE 98-2029, 027-1c1) was mixed in artificial seawater (70L) to inoculate oysters (n=35) at 4-5 log MPN/g. Inoculated oysters were subjected to depuration with feed (algae=0.036ml/gram of oyster) and without feed at 12.5 degrees C. Oysters (n=5) were analyzed for V. parahaemolyticus using a three-tube MPN method after 0, 1, 3, 5, and 6days of depuration. Depuration (6days) achieved average V. parahaemolyticus reductions of 2.75 log MPN/g and 3.03 log MPN/g in the fed and unfed systems, respectively; however, feeding status did not significantly impact the efficacy of depuration to reduce V. parahaemolyticus in Pacific oysters. Further optimization of depuration is necessary to achieve the regulatory target for V. parahaemolyticus decontamination in raw oysters.