Abundance of Vibrio cholerae, V. vulnificus, and V. parahaemolyticus in Oysters (Crassostrea virginica) and Clams (Mercenaria mercenaria) from Long Island Sound
ABSTRACTVibriosis is a leading cause of seafood-associated morbidity and mortality in the United States. Typically associated with consumption of raw or undercooked oysters, vibriosis associated with clam consumption is increasingly being reported. However, little is known about the prevalence ofVibriospp. in clams. The objective of this study was to compare the levels ofVibrio cholerae,Vibrio vulnificus, andVibrio parahaemolyticusin oysters and clams harvested concurrently from Long Island Sound (LIS). Most probable number (MPN)–real-time PCR methods were used for enumeration of totalV. cholerae,V. vulnificus,V. parahaemolyticus, and pathogenic (tdh+and/ortrh+)V. parahaemolyticus.V. choleraewas detected in 8.8% and 3.3% of oyster (n= 68) and clam (n= 30) samples, with levels up to 1.48 and 0.48 log MPN/g in oysters and clams, respectively.V. vulnificuswas detected in 97% and 90% of oyster and clam samples, with median levels of 0.97 and −0.08 log MPN/g, respectively.V. parahaemolyticuswas detected in all samples, with median levels of 1.88 and 1.07 log MPN/g for oysters and clams, respectively. The differences betweenV. vulnificusand total and pathogenicV. parahaemolyticuslevels in the two shellfish species were statistically significant (P< 0.001). These data indicate thatV. vulnificusand total and pathogenicV. parahaemolyticusare more prevalent and are present at higher levels in oysters than in hard clams. Additionally, the data suggest differences in vibrio populations between shellfish harvested from different growing area waters within LIS. These results can be used to evaluate and refine illness mitigation strategies employed by risk managers and shellfish control authorities.