Phenotypic and genotypic characterization of vancomycin-resistant Enterococci from clinical isolates

Although Enterococci are part of the normal flora of the gastrointestinal tract in humans, they cause infections under certain circumstances. Vancomycin Resistant Enterococci (VRE) cause serious problems resulting in limited therapeutic options in hospitalized patients. In this study we examined the VRE isolated from clinical specimens to determine the prevalence of vanA and vanB phenotypes. Thirty-two vancomycin resistance Enterococci isolates cultured from clinical samples were investigated. Resistance of isolates to vancomycin, teicoplanin, tetracycline, gentamicin,erythromycin and ciprofloxacin were determined by disk diffusion method. MIC of vancomycin for all strains was determined using by micro-dilution method. Existence of vanA and vanB genes was checked by PCR. Using microbroth dilution assay, 25 and 5 isolates appeared as vanA and vanB phenotypes respectively. All isolates were resistance to ciprofloxacin. Resistance to erythromycin, tetracycline and gentamicin were detected in 96.87%, 81.25% and 78.12% of isolates respectively. vanA and vanB genes were found in 25 and 6 isolates respectively. Co-existence of vanA and vanB were found in 13 isolates using PCR. Our results showed that 12 and 6 of the strains are phenotypically and genotypically vanA and vanB respectively. Although 13 of 25 isolates (52%) showed vanA phenotype, they have both vanA and vanB genes. With the possibility of genotypically alteration in enterococci, it seems that these isolates acquired vanB gene through conjugation.