Investigation of vancomycin resistance genes in Enterococcus species isolated from bovine mastitis

The aim of the present study was to isolate Enterococcus species from mastitis in cows, investigate the vancomycin resistance genes in the isolated species using PCR, and determine the antibiotic resistance of VRE strains to some antibiotics commonly used in Turkey. A total of 512 mammary quarter milk samples from 150 lactating cows were used. Following phenotypic typing by a commercial identification kit, multiplex PCR was applied to the strains using species specific primers. The Enterococcus isolation rate was found to be 13.9% (n=71). The most frequently isolated species was E. faecalis (n=40, 56.3%), followed by E. faecium (n=16, 22.5%), E. solitarius (n=6, 8.5%), E. durans (n=5, 7.1%) and E. hirae (n=4, 5.6%). Of 71 Enterococcus strains, 19 (26.7%) were determined to be VRE. While a total of five vanA (7%), 10 vanB (14%) and 12 vanC2/C3 (16.9%) genes were detected in the strains, none of the strains harbored the vanC1 gene. The vancomycin resistance gene was not found in any E. solitarius strain. While all of the VR 19 strains were phenotypically resistant to vancomycin and fusidic acid, high resistance rates were also determined in the strains to streptomycin (84.2%), erythromycin (73.7%), tetracycline (68.4%), penicillin G (68.4%), gentamicin (68.4%), lincomycin (57.9%), cephalothin (52.6%) and kanamycin (52.6%). Consequently, it was thought the VRE positive mastitic milk samples may comprise a potential risk for public health. To our knowledge, this is the first study showing the presence of VRE in milk with mastitis by PCR in Afyonkarahisar.