Oyster processing strategies for eliminating Vibrio parahaemolyticus and Vibrio vulnificus from New Hampshire oysters

Introduction Vibrio parahaemolyticus (Vp) and Vibrio vulnificus (Vv) are human pathogens commonly associated with bivalve shellfish. These Vibrios cause infections to humans when patients consume raw or undercooked shellfish or when it’s in free-living form in estuarine environments. There are three clinical manifestations of disease caused by Vp and Vv; most common for Vp is gastroenteritis and rarely causing wound infections and septicemia and Vv causes more wound infections and septicemia than gastroenteritis. In order to provide consumers with safe raw oysters, shellfish companies have implemented post-harvest strategies to remove Vibrios within the oysters. However, these methods to remove the Vibrio species from the oysters can be relatively expensive and typically kill the oysters. The main focus of this study was to investigate a range of depuration and relaying strategies for reducing Vp and Vv levels in oysters. The first objective was to adopt published real-time PCR, complemented with Most-Probable-Number (qPCR-MPN), methods to detect Vp and Vv from enriched oyster homogenate instead of using culture-based identification methods. The main focus was to conduct relay and depuration experiments from warm to cold seasons under controlled and natural environmental conditions. The final objective was detection of pathogenic strains of Vp, strains of Vp containing the thermostable direct hemolysin (tdh) and TDH-related hemolysin (trh) in pre-temperature abused oysters and temperature abused oysters.