Antibiotic resistance profiling and genotyping of vancomycin-resistant enterococci collected from an urban river basin in the Provincial City of Miyazaki, Japan

The distribution characteristics of vancomycin-resistant enterococci (VRE) and the resistance of enterococcus isolates to various antibiotics were investigated in Yae River, which flows through Miyazaki city, Japan. The prevalence of VRE among specimens collected from the urban river basin using mEI agar was 0.9% (2 of 226 enterococcal isolates). In the 333 enterococcal isolates obtained using mEI agar or vancomycin-supplemented mEI agar, the possession of the vancomycin-resistant genes (vanA, vanB, vanC1, and vanC2/C3) was examined using multiplex PCR analysis. Although VRE possessing vanA and vanB were not detected in any isolates, isolates possessing vanC2/C3 were detected at all sampling sites and on all days. All isolates (101 strains) possessing vanC2/C3 that were obtained on vancomycin-supplemented mEI agar were identified as E. casseliflavus and analyzed for genotypes using pulse-field gel electrophoresis (PFGE) analysis. These E. casseliflavus isolates revealed them to be genetically highly divergent strains, suggesting that many contamination sources were present in this study area. Many of the enterococcal isolates obtained were resistant to erythromycin, ciprofloxacin, and tetracycline; enterococci distributed in the studied urban river basin are resistant to universally applicable antibiotics. These results indicate that VRE carrying vanC2/C3 are distributed in Yae River, and the sources of VRE are scattered across the river basin.