Genetic Characterisation of Antibiotic Resistance and Virulence Factors in VanA-containing Enterococci from Cattle, Sheep and Pigs Subsequent to the Discontinuation of the Use of Avoparcin

The prevalence of vancomycin resistant-enterococci (VRE) in faecal samples from cattle, sheep and pigs slaughtered for human consumption was evaluated. Enterococci containing the vanA gene were detected in 25.3% and 2.7% of the porcine and ovine samples, respectively, and were identified as Enterococcus faecium. No vanA-containing enterococcal strains were detected in bovine samples. Enterococcal strains with intrinsic vancomycin resistance were detected in seven (9.9%) faecal samples from pigs and in two samples from both cattle and sheep (3.7% and 2.7%, respectively). All vanA-positive isolates from pigs were resistant to tetracycline and erythromycin, and the mobile element Tn916/Tn1545-like transposon was detected in 90.5% of the tetracycline-resistant isolates that contained the tet(M) gene. Although gelatinase and haemolytic activity were not detected, the hyl and cylB virulence genes were found within the VRE strains isolated.