Molecular characterization of vancomycin-resistant Enterococcus faecium isolated from intensive care units.

To assess the molecular characterization of disseminated vancomycin-resistant enterococci (VRE) in the intensive care units, 546 enterococci isolates were collected from different clinical samples in a prospective observational study. The results showed that a total number of 33 isolates (6 %) were resistant to vancomycin. Most of the VRE isolates 11 (34 %) were isolated from intensive care units (ICUs). 18 (55 %) VRE isolates were obtained from urinary tract infections. The results from pulsed-field gel electrophoresis showed five common types (CT) and 13 single types (ST) among the VRE isolates. The analysis showed two and one major CTs and ST among the ICUs isolates, respectively. Tn1546 transposon was analyzed using ClaI-digested long PCR (L-PCR) RFLP followed by sequencing. The results showed the presence of two different lineages of transposon among the two clonal groups. Lineage 1 with the arrangement of Tn1546 prototype in the first clonal group and the second lineage with 13 kb harboring two insertion sequences, IS1216 V and IS1542. DNA hybridization showed that vanA gene in all VRE isolates, with an exception of one isolate, was present in the same location on the genome. Overall, the results suggest that a few VRE clonal types were disseminated in ICUs in hospitals in Iran which were able to transfer their vanA with high conjugation frequency.