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

Abstract

The aim of the present study was to evaluate the presence of <i>Salmonella</i> spp., verotoxigenic <i>E. coli</i> (VTEC), <i>Vibrio</i> spp., and Norovirus GI-GII in bivalve molluscs, cockles, and European grooved carpet shells (<i>Cerastoderma</i> spp. and <i>Ruditapes decussatus</i>) collected from a class B growing natural bed in Sardinia (Italy). All of the samples were analysed for <i>Salmonella</i> spp. detection according to European Commission Regulation (EC) 2285/2015. Detection and enumeration of <i>Vibrio</i> spp. were performed according to previously published methods. Presumptive identification of <i>Vibrio</i> spp. isolates was performed by means of conventional biochemical tests. <i>E. coli</i> 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 <i>Salmonella</i> spp. were detected. The prevalence of <i>Vibrio</i> spp. was 90%, and the average contamination levels were 3.19 ± 1.07 and 2.84 ± 0.31 Log₁₀ cfu/g in cockles and European grooved carpet shells, respectively. The prevalence of <i>E. coli</i> 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 <i>E. coli</i> VTEC, pathogenic vibrios, and Norovirus. The presence of such pathogens in shellfish is of major concern for the safety of consumers.