The Eastern oyster (Crassostrea virginica) is consumed raw by nearly twenty million Americans and can filter approximately five to twenty-five liters of water per hour while accumulating various disease-causing contaminants within its tissues. These diseases are more likely to be caused by bacteria, as they contribute to most seafood-borne infections. Sally Cove in Rehoboth Bay (Longitude: Latitude; 075˚ 07.631’ W: 38˚ 38.932’ N) is one of the oyster aquaculture farms along the Atlantic coast of Delaware that produces oysters through off-bottom and bottom cultures for consumption in Delaware. However, the risk of bacterial contamination from consuming raw oysters from this farm is unknown. The objective of this study was to evaluate the presence and persistence of diverse bacteria in seawater and oysters from off-bottom and bottom cultures at Sally Cove. A control site within Sally Cove that is without oyster cultures was included in this study.
Six liters of seawater and twelve oysters each from the off-bottom and bottom cultures at Sally Cove and six liters each of off-bottom and bottom seawater from the control site were collected once per month from July to October 2023. The seawater and oysters were processed, pre-enriched, and cultured on selective media to obtain colonies of targeted bacteria.
Molecular confirmation (Figure 1) with PCR and rt-PCR showed that Vibrio parahaemolyticus, Shiga-toxin-producing Escherichia coli, Salmonella enterica, Shigella spp., Staphylococcus aureus, and Pseudomonas aeruginosa were present and persisted in seawater and oysters from both cultures at the farm throughout the study. These findings indicate that consuming raw oysters from Sally Cove poses contamination risks from several bacteria, predominantly in summer months.