The Eastern oyster (Crassostrea virginica) is a popular seafood choice in the USA, consumed raw by nearly 20 million Americans. These oysters filter approximately five liters of water per hour while accumulating various contaminants from seawater within their bodies. Pathogenic bacteria have been detected in various seafood, including oysters, and have led to numerous reported foodborne illnesses. Sally Cove in Rehoboth Bay (Longitude: Latitude; 075˚ 07.631’ W: 38˚ 38.932’ N) is one of the principal habitats and aquaculture sites for oysters along the Atlantic coast in Delaware, where oysters are produced through suspended and bottom cultures for both commercial and ecological purposes. However, agricultural practices and human activities in Delaware elevate the risk of microbial contamination within the Delaware Inland Bays, which were previously reported to have contained high levels of bacteria. The objective of this study was to detect and compare the presence of ten pathogenic bacteria in seawater and oysters from the suspended and bottom oyster cultures in Sally Cove in Rehoboth Bay, Delaware. For comparison, a site without oysters (Sally Cove control) within Sally Cove was selected as a control.
Triplicates of seawater (8.0 L) and oysters were sampled from suspended (0.10 m) and bottom (1.80 m) cultures once across four months, from July through October 2023. Seawater was centrifuged to obtain the sediment containing environmental DNA (eDNA) while the oysters were washed and shucked, and their interval vular fluid and tissues were homogenized and pre-enriched in buffered peptone water or tryptic soy broth for culturing . Bacteria were detected using polymerase chain reaction (PCR) and gel electrophoresis with bacteria-specific primers (Figure 1). Preliminary findings revealed the presence of Vibrio parahaemolyticus, Escherichia coli, Listeria monocytogenes , and Clostridium species in seawater and oysters sampled in July and August from both suspended and bottom cultures at Sally Cove and the control site. In conclusion , consuming raw oysters from Sally Cove during summer may pose risks of
contamination of these pathogenic bacteria.
Keywords: Crassostrea virginica, pathogenic bacteria, detection, molecular biology.