Presence, seasonal distribution and biomolecular characterization of Vibrio parahaemolyticus and Vibrio vulnificus in shellfish harvested and marketed in Sardinia (Italy) between 2017 and 2018.

In the present study, we aimed to investigate the presence, seasonal distribution and biomolecular characterization of Vibrio parahaemolyticus and Vibrio vulnificus in samples of bivalve molluscs ( Mytilus galloprovincialis, Crassostrea gigas, Ruditapes decussatus, Venus verrucosa and Solen vagina ) and gastropod molluscs (Murex brandaris) harvested and marketed in Sardinia (Italy) between 2017 and 2018. A total of 444 samples were submitted to qualitative determination of Vibrio spp., V. parahaemolyticus and V. vulnificus. Identification and virulence profile of the isolated strains were performed by biomolecular methods. The overall prevalence of Vibrio spp. was 7%. The highest prevalence was pointed out in R. decussatus (8.3%). The prevalence of V. parahaemolyticus and V. vulnificus were 2.7% and 4.7% respectively. Higher levels of V. parahaemolyticus and V. vulnificus prevalence were highlighted in R. decussatus (4.2%) and C. gigas (6.2%) respectively. Potentially pathogenic V. parahaemolyticus strains were a minority ( n. 2 isolates tdh-/trh+ and n. 1 isolate tdh+/trh- ) and were recovered from M. galloprovincialis . None of the isolates was tdh+/ trh+. Pathogenic Vibrios infections are often underestimated and the reports of human infections in Europe are constantly increasing. European data on the true distribution of Vibrionaceae are scarce: the results of the present study highlight the need of constant monitoring plans to update the distribution of potentially pathogenic Vibrios.