Identification of enterococci and isolation of vancomycin-resistant strains in Spanish cheeses

Enterococci are currently the third most common bacterial pathogen associated with nosocomial infections, after staphylococci and Escherichia coli, and resistance by enterococci to extant antibiotics therefore represents a health threat. Thirty commercial Spanish bovine, ovine, and caprine cheeses (10 each) were screened for the presence of vancomycin-resistant enterococci (VRE). All enterococcal strains isolated were identified using rep-PCR and multiplex PCR molecular assays, and the following species identifications were made: Enterococcus faecium, E. faecalis, E. durans, E. hirae, and E. pseudoavium. Enterococcal species variability was highest in the cheeses made from all the raw milks (bovine, ovine, and caprine) and from pasteurized caprine milk, though the incidence of VRE in the cheeses considered was low. Only three VRE strains were found, all from a single cheese sample, two being identified as vanA-carrying E. faecalis strains and the other being identified as a vanB-carrying E. faecium strain.