Clonal dissemination of vanA positive Enterococcus species in tertiary care hospitals in Karachi, Pakistan.

OBJECTIVE To perform molecular typing of vancomycin resistant Enterococcus spp. (VRE) strains endemic in various hospitals of Karachi, to characterize the mechanism of glycopeptide resistance and assess the genetic relatedness, for understanding its transmission locally. METHOD This was a cross sectional study conducted in the clinical and research laboratory of Aga Khan University Hospital (AKUH), Karachi, Pakistan from October 2007 to September 2008. Non-duplicate 86 (65 AKUH and 21 non-AKUH) VRE strains were included. Molecular typing of nosocomial isolates of VRE was carried out by using Pulsed field gel electrophoresis (PFGE) and identification of vanA and vanB genes were performed by conventional Polymerase Chain Reaction (PCR). RESULTS Analysis of PFGE data by Tenover scheme showed single major pulsotype A with its subtypes A1, A2 and A3 present among different tertiary hospitals in Karachi. The dice coefficient of similarity among AKUH, non-AKUH and total 86 (AKUH and non-AKUH) had a value of 90%, 88% and 89% reflecting their clonal relatedness. In all 60/65 (92%) and 19/21 (90%) AKUH and non-AKUH isolates had vanA gene respectively. None had vanB gene. CONCLUSION Molecular typing suggested that VRE isolates had same clonal origin indicating nosocomial transmission. Institution of strict infection control measures with active surveillance should be taken to avoid its further spread.