Evaluation of food safety criteria in Cerastoderma spp. and Venerupis decussatus collected in Sardinia (Italy)

The aim of the present study was to evaluate the food safety criteria of bivalve molluscs collected from a class B Sardinian growing natural bed. Samples from four batches of cockles (Cerastoderma spp.) and grooved carpet... [ view full abstract ]

The aim of the present study was to evaluate the food safety criteria of bivalve
molluscs collected from a class B Sardinian growing natural bed. Samples from four batches of cockles (Cerastoderma spp.) and grooved carpet shells (Venerupis decussatus) were collected and analyzed with traditional and molecular methods. All the samples were analyzed for Salmonella spp. detection according to Reg. (EC) 2073/2005 using ISO/TS 16649–3. Presence of L.monocytogenes and Vibrio spp. was performed following ISO 11290-1:1996 and ISO 6887-1: 2004. A multiplex PCR screening test for the direct detection of E.coli VTEC has been applied. Norovirus GI and GII have been determined by RT-PCR. The prevalence of E.Coli VTEC by direct PCR screening test was 6.6%. According to the multiplex PCR, the DNA from two enrichment broths showed a complete virulence profile, instead in all the strains isolated by culture methods any virulence genes were detected. The low prevalence of E. coli VTEC does not correlate with the presence of naturally occurring Vibrios (90%). The average contamination levels were 3.19±1.07 and 2,84±0,31 Log10 cfu/g in cockles and grooved carpet shells respectively. The presence of Norovirus has been highlighted in 25% of grooved carpet shells samples. The prevalence of NoV GII and GI was 25% and 10% respectively. Results showed the typical microbiological profile of bivalve molluscs collected from backwaters and confirmed the capability of shellfish in accumulating pathogenic E.coli VTEC, vibrios and Norovirus. The presence of such pathogens in bivalve molluscs is of major concern for the safety of consumers.