Identification and safety assessment of enterococchi isolated from a Sardinian ewe's raw milk pdo cheese (Fiore Sardo)

The aim of this study was to identify enterococcal microflora and to assess some safety aspects (presence of antibiotic resistance traits and virulence determinants) ofEnterococcusspecies colonizing Sardinian traditional ewe’s milk dairy products. Fiore Sardo cheese was chosen as ‘model’ to carry out this study.Thus, 322 enterococci isolated from 21 artisanally produced Fiore Sardo cheese samples were genotipically characterised at species level by species-specific PCR and 16S rDNA sequencing, and at strain level by cluster analysis of rep-(GTG)5PCR, RAPD M13 PCR, and PFGE patterns. Five enterococcal species, two dominant (E. faeciumandE. faecalis) and three less-abundance (E. durans, E. Hirae, andE. Gallinarum) were found. A high biodiversity at strain level was found for the dominant species.The incidences of resistance to 14 antibiotics was phenotypically tested. The presence of genes encoding for tetracycline and erythromycin resistance and for 8 virulence factors was investigated. Different results were obtained especially depending on the medium of origin (with or without antibiotics) of isolates. The incidence of antibiotic resistance and virulence determinants genes was higher forE. Faecalisisolates.The results presented in this work were consistent with those reported in literature for food enterococcal isolates suggesting that their presence in Sardinian dairy foods does not represent a threat to human health.