Molecular epidemiology of vancomycin-resistant enterococci isolated from non-tertiary-care and tertiary-care hospitals in Korea.

Abstract

This study compared the molecular characteristics of vancomycin-resistant

Enterococcus faecium (VREF) isolates recovered from 20 non-tertiary-care

hospitals (36 isolates) and three tertiary-care hospitals (26 isolates) in

diverse geographical areas of Korea from October 2010 to April 2011. All isolates

carried the vanA gene only, but 42% and 73% of non-tertiary and tertiary-care

isolates expressed the VanB phenotype (teicoplanin minimum inhibitory

concentration 16 mug/ml). All isolates harboured insertion sequences, IS1542 and

IS1216V, within Tn1546. The isolates from tertiary-care hospitals tended to have

reduced Tn1546 lengths by deletion of sequences adjacent to IS elements.

Multilocus sequence typing revealed eight sequence types within clonal complex 17

(CC17), but DNA fingerprinting by rep-PCR did not show clonal relatedness between

the intra- and inter-hospital isolates. These results suggest that vanA, which

has prevailed in tertiary-care hospitals of Korea since the 1990s, had been

transferred horizontally to non-tertiary-care hospitals while the genetic

rearrangement driven by evolutionary adaptation to adverse environments may have

occurred in tertiary-care hospitals.