Survey on the presence of enterovirulent Escherichia coli, including E. coli O157, in cheese manufactured in the Italian alpine region

The aim of the present study was to investigate the prevalence of enterovirulent Escherichia coli strains in cheese manufactured in the Italian Alpine Region. Cheese samples obtained from raw and pasteurised milk were collected from cheese-making plants. Enumeration of E. coli and the presence of verocytotoxigenic (VTEC), enteropathogenic (EPEC) and enterotoxic (ETEC) E. coli were carried out. A multiplex-PCR for the amplification of the sequences of VT1, VT2, eae, ehxA, ST, LT genes was used to identify pathogenic E. coli strains. The presence of E. coli O157 was investigated using an immunomagnetic separation technique. E. coli 0 157 was not recovered in cheese made from raw or pasteurised milk. The multiplex PCR approach detected at least one virulence determinant in only ten cheese samples, in four of them, a verotoxin-producing gene (VT2 and/or VT1) was detected and in the remaining six only the attaching and effacing lesion genes (eae) were found. No ETEC strains were detected. The statistical analyses of the results demonstrated significant associations between the use of raw milk in cheese production and the presence of detectable virulence genes in cheese. Moreover, high E. coli counts were also associated with the use of raw milk in fresh and ripened cheese production. The results revealed the survival and recovery of pathogenic strains even after a 60-day ripening period, highlighting the importance of the hygienic and sanitary requirements for milk used in the production of both fresh and ripened cheese.