Background: Enterococcus faecium has emerged as an important nosocomial pathogen worldwide, and this trend has been associated with the dissemination of a genetic lineage designated clonal complex 17 (CC17). In the present study, characterization of the glycopeptide resistance mechanism, genetic relatedness, and pathogenicity in isolates of vancomycin-resistant E. faecium in the Chungcheong area were investigated. 

Methods: A total of 37 consecutive, non-duplicate, vancomycin-resistant E. faecium were isolated at three university hospitals in the Chungcheong area. The mechanism of glycopeptide resistance and pathogenicity factors were studied using PCR, and the genetic relatedness was determined via multilocus sequence type and esp repeat profile analysis. Additionally, the quinolone resistance-determining regions of parC and gyrA were sequenced to identify mutations involved in ciprofloxacin resistance. 

Results: Two genotypes of VRE were confirmed: VanA- phenotype vanA genotype VRE (25 isolates) and VanB-phenotype vanA genotype VRE (12 isolates). MLST analysis revealed five sequence types. A significant result was that ST414 and CNS4 (4-1- 1-1-1-1-1) were considered as belonging to CC17. The esp and hyl genes were found in 100% and 86.4% of the isolates, respectively. A total of 37 isolates showed genetic mutations in parC and gyrA. 

Conclusion: All isolated strains in the present study belonged to one of the CC17 genotypes including ST414 and CNS4 (4-1-1-1-1-1-1), which were not previously detected in Korea. The combination of MLST and the esp gene repeat profiles can be useful for genetic characterization of VREF isolates with regard to the evolutionary process and epidemiology of the clones. (Korean J Clin Microbiol 2011;14:60- 66)