Occurrence, Seasonal Distribution, and Molecular Characterization of Vibrio vulnificus, Vibrio cholerae, and Vibrio parahaemolyticus in Shellfish (Mytilus galloprovincialis and Ruditapes decussatus) Collected in Sardinia (Italy)

In this study, we investigated the occurrence, seasonal distribution, and molecular characterization of pathogenic vibrios in Mediterranean mussels (Mytilus galloprovincialis) and grooved carpet shells (Ruditapes decussatus) from two harvesting areas of Sardinia (Italy). Samples collected before and after depuration were submitted for qualitative and quantitative determination of Vibrio spp. Vibrio spp. isolates were presumptively identified by means of biochemical methods. Identification and virulence profile of Vibrio cholerae, Vibrio parahaemolyticus, and Vibrio vulnificus were performed by molecular methods. The prevalence of Vibrio spp. in M. galloprovincialis and R. decussatus was, respectively, 96 and 77%. The averaged enumeration (mean 6 standard deviation) of Vibrio spp. in samples of M. galloprovincialis and R. decussatus collected at the harvesting time was 2.04 +/- 0.45 and 2.51 +/- 0.65 log CFU/g, respectively. The average contamination levels in samples collected after purification were 2.28 +/- 0.58 log CFU/g (M. galloprovincialis) and 2.12 +/- 0.67 log CFU/g (R. decussatus). Four potentially pathogenic V. parahaemolyticus isolates (tdh(+) or trh(+)) were recovered from grooved carpet shells samples. No isolate was tdh(+)/trh(+). The presence of potentially pathogenic vibrios in Sardinian waters strengthens the need for rational purification practices under controlled conditions to guarantee the protection of consumers. HIGHLIGHTS Occurrence and pathogenicity characteristics of Vibrio pathogens were investigated. Prevalence of Vibrio spp. in M. galloprovincialis was 96% and in R. decussatus was 77%. Environmental conditions influence the occurrence of Vibrio spp. Four V. parahaemolyticus isolates carried tdh or trh genes. Rational purification practices are needed to guarantee the protection of consumers.