Investigation of phenotypic and genotypic characteristics of vancomycin-resistant Enterococcus faecium isolates

Abstract

The purpose of the present study was to investigate the phenotypic and genotypic characteristics and the probable clonal dissemination of 13 vancomycin-resistant enterococcus (VRE) strains isolated between February-August 2006 from 11 patients at the Hospital of Istanbul Faculty of Medicine. The in vitro activities of antibiotics were determined by disk diffusion method in accordance with the CLSI (Clinical and Laboratory Standards Institute) guidelines and the minimum inhibitory concentration (MIC) values by E-test. Multiplex polymerase chain reaction (PCR) was performed for detection of vanA, vanB and vanC genes and RAPD-PCR (Randomly amplified polymorphic DNA-PCR) for investigating a clonal relationship among the isolates. All isolates exhibited resistance to vancomycin, teicoplanin, ampicillin, and high-level resistance to streptomycin. VanA phenotype and the relevant vanA gene, characterised by resistance to both vancomycin and teicoplanin, were detected in all isolates which were all E. faecium. Molecular investigation by RAPD-PCR showed these strains to belong to four different patterns, each containing 1 to 5 isolates. According to these results, the spread of VRE within our hospital was considered as a polyclonal dissemination.