Vancomycin-resistant enterococci (VRE) in meat and environmental samples

Abstract

We investigated the spread of vancomycin-resistant enterococci (VRE) in strains from meat and environmental samples and the location of glycopeptide-resistance determinants in VanA isolates. VRE and VSE (vancomycin-sensitive enterococci) resistance patterns to six antimicrobials were also evaluated. A total of 59 meat isolates (35%) and 119 environmental isolates (26.5%) were glycopeptide resistant enterococci. In particular, 10.7% meat isolates belonged to the VanA, 8.3% to VanB and 16% to VanC phenotypes. Environmental samples presented 0.7% VanA, 14.5% VanB, and 11.4% VanC strains. Evident differences were not observed among the resistance patterns of VRE and VSE isolates. Neither an important difference was observed comparing the resistance patterns in enterococci from meat and environment. In particular a low incidence of β-lactamic resistant strains was found, whereas high rates of resistance were observed for streptomycin (85.7% and 92.8%), kanamycin (79.7% and 96%) and gentamycin (85.1% and 91.7%). An intermediate rate of resistant bacteria emerged for erythromycin (35.1% and 10.5%). All VanA isolates independent of origin had more plasmids with different molecular weights. PCR amplification of the 732 bp fragment in plasmids from the VanA strains confirmed affiliation to the vanA gene cluster and the extrachromosomal location of the glycopeptide-resistance determinants. Our study suggests that food and environment play a potential role as reservoirs of resistance determinants, prompting the need to undertake epidemiological and molecular studies to evaluate the mobility of these genes.