Genetic characterization of a VanG-type vancomycin-resistant Enterococcus faecium clinical isolate

Abstract

Objectives: To characterize, phenotypically and genotypically, the first Enterococcus faecium clinical isolateharbouring a vanG operon.Methods: The antibiotic resistance profile of E. faecium 16-346 was determined and its whole genomesequenced using PacBio technology. Attempts to transfer vancomycin resistance by filter mating were performedand the inducibility of expression of the vanG operon was studied by reverse-transcription quantitativePCR (RT-qPCR) in the presence or absence of subinhibitory concentrations of vancomycin.Results: E. faecium 16-346 was resistant to rifampicin (MIC>4 mg/L), erythromycin (MIC>4 mg/L), tetracycline(MIC>16 mg/L) and vancomycin (MIC 8 mg/L), but susceptible to teicoplanin (MIC 0.5 mg/L). The strain harbouredthe vanG operon in its chromosome, integrated in a 45.5 kb putative mobile genetic element, similarto that of Enterococcus faecalis BM4518. We were unable to transfer vancomycin resistance from E. faecium16-346 to E. faecium BM4107 and E. faecalis JH2-2. Lastly, transcription of the vanG gene was inducible byvancomycin.Conclusions: This is, to the best of our knowledge, the first report of a VanG-type vancomycin-resistant strain ofE. faecium. Despite the alarm pulled because of the therapeutic problems caused by VRE, our work shows thatnew resistant loci can still be found in E. faecium.