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LEVELS OF Vibrio parahaemolyticus IN RAPIDLY COOLED OR REFRIGERATED PACIFIC OYSTERS Crassostrea gigas COLLECTED IN WASHINGTON STATE IMMEDIATELY AFTER HARVEST, AND FOLLOWING AMBIENT AIR EXPOSURE

Whitney A. Jaillet*, Clara H. Hard, Laura W. Johnson, and Jessica L. Jones
 
 FDA, Gulf Coast Seafood Laboratory
 1 Iberville Dr.
 Dauphin Island, AL 36528
 Whitney.Jaillet@fda.hhs.gov

Vibrio parahaemolyticus is the leading cause of seafood-related infections in the United States, and is usually associated with consumption of raw or undercooked shellfish. As a result of these illnesses, vibrio control plans have been implemented in several states in order to mitigate vibrio related sickness during the warmest months of the year when there is a heightened risk of illness. In Washington State, the vibrio control plan assigns risk categories to various harvesting areas, and requires time to cooling guidelines that range from 1h to 9h post-harvest. This study examines the effects of these post-harvest handling practices on the levels of V. parahaemolyticus in Pacific oysters.

During the months of July and August, eight treatment groups were harvested five times from Totten Inlet in South Puget Sound, WA and shipped to the FDA Gulf Coast Seafood Laboratory in Dauphin Island, AL for analysis. Briefly, each of the eight treatment groups were tested in triplicate with a standard 3-tube MPN in Alkaline Peptone Water (APW). Positive MPN tubes were tested with Real-Time PCR (Rti-PCR) for total V. parahaemolyticus (tlh gene), and pathogenic V. parahaemolyticus (tdh and trh genes). Results of the Rti-PCR were scored with a standard MPN table to determine estimates. The eight treatment groups evaluated include:  Initial harvest, initial harvest followed immediately by icing, 1h, 5h, and 9h ambient storage followed by icing, and 1h, 5h, and 9h ambient storage followed by refrigeration.  

Preliminary results suggest that cooling via icing or refrigeration had no effect on the total or pathogenic V. parahaemolyticus levels. Levels of total and pathogenic V. parahaemolyticus were not appreciably affected by one hour of ambient air exposure, but five or nine hours of exposure resulted in an increase in total and pathogenic V. parahaemolyticus of >1 log (Fig. 1). These data highlight the need for effective temperature controls, and have the potential to impact current handling practices.




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