Determination of Salmonella spp., E. coli VTEC, Vibrio spp., and Norovirus GI-GII in Bivalve Molluscs Collected from Growing Natural Beds in Sardinia (Italy)

The aim of the present study was to evaluate the presence of spp., verotoxigenic (VTEC), spp., and Norovirus GI-GII in bivalve molluscs, cockles, and European grooved carpet shells ( spp. and ) collected from a class B growing natural bed in Sardinia (Italy). All of the samples were analysed for spp. detection according to European Commission Regulation (EC) 2285/2015. Detection and enumeration of spp. were performed according to previously published methods. Presumptive identification of spp. isolates was performed by means of conventional biochemical tests. VTEC was isolated following a direct multiplex polymerase chain reaction (PCR) screening test. Norovirus GI and GII were determined by reverse transcriptase-polymerase chain reaction (RT-PCR). No spp. were detected. The prevalence of spp. was 90%, and the average contamination levels were 3.19 ± 1.07 and 2.84 ± 0.31 Log cfu/g in cockles and European grooved carpet shells, respectively. The prevalence of VTEC was 6.6%. All of the isolates showed a complete pathogenicity profile. The presence of Norovirus was highlighted in 25% of European grooved carpet shells samples. Results showed the typical microbiological profile of bivalve molluscs collected from backwaters and confirmed the capability of shellfish to accumulate VTEC, pathogenic vibrios, and Norovirus. The presence of such pathogens in shellfish is of major concern for the safety of consumers.