Scientific Publications by FDA Staff

Appl Environ Microbiol 2014 Dec 15;80(24):7667-72

Vibrio cholerae, V. vulnificus, and V. parahaemolyticus Abundance in Oysters (Crassostrea virginica) and Clams (Mercenaria mercenaria) from Long Island Sound.

Jones JL, Ludeke CH, Bowers JC, DeRosia-Banick K, Carey DH, Hastback W

Vibriosis 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 reported. However, little is known about the prevalence of Vibrio spp. in clams. The objective of this study was to compare the levels of V. cholerae, V. vulnificus, and V. parahaemolyticus in oysters and clams harvested concurrently from Long Island Sound (LIS). MPN-real-time PCR methods were used for enumeration of total V. cholerae, V. vulnificus, V. parahaemolyticus, and pathogenic (tdh+ and/or trh+) V. parahaemolyticus. Vibrio cholerae was 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. Vibrio vulnificus was detected in 97% and 90% of oyster and clam samples, with median levels of 0.97 and -0.08 log MPN/g, respectively. Vibrio parahaemolyticus was detected in all samples with median levels of 1.88 and 1.07 log MPN/g for oysters and clams, respectively. The differences between V. vulnificus and total and pathogenic V. parahaemolyticus levels in the two shellfish species were statistically significant (P<0.001). These data indicate that V. vulnificus, and total and pathogenic V. parahaemolyticus are more prevalent and at higher levels in oysters than hard clams. Additionally, the data suggests 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.