The prevalence and molecular characterization of vancomycin resistant gram positive cocci isolated from patients in Tehran

Gram positive bacteria, particularly, Staphylococcus aureus, coagulase negative staphylococci and enterococci are of particular concern in hospitals. But there has been increasing concern about the development of vancomycin resistant enterococci and MRSA strains with reduced susceptibility to vancomycin over the last decade. Therefore, the present study was carried out to confirm the identification of vancomycin resistant gram positive cocci, to determine antibiotic resistance pattern and tostudy vancomycin resistance genes. The isolates from clinical samples were collected from hospitalized patients and outpatients in Tehran. Gram positive cocci species identification was performed by using conventional tests and PCR using specific primers. VRE isolates were subjected to antibiotic susceptibility testing, MICs of vancomycin were determined by the E-test method. Determination of vancomycin resistance genes, vanA and vanB were performed with PCR. Confirmation of transposons was performed with specific primers for vanS. Out of 1030 gram positive isolates, none of the staphylococci or streptococci isolates were resistant to vancomycin. Most of vancomycin resistant isolates in this study were VRE. faecium (96%) and harbored vanA. All of the isolates were positive for vanS the conserved fragment of transposon and carried the identical digestion pattern like type strain. According to the results of this study, all of the vancomycin resistant isolates were enterococcus spp. Vancomycin resistant enterococci itself is now a major and largely untreatable infection, and can pass the vancomycin resistance genes to the other highly virulent gram positive cocci.