A total of 98 vancomycin-resistant Enterococcus faecium (VREF) isolates from four tertiary-care hospitals in Korea during the period between 1998 and 2004 were analyzed for genotypic characteristics using the multiplex PCR, multilocus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE), and esp gene analysis. Ninety-two isolates of VREF with VanA phenotype and five of six isolates with VanB phenotype possessed the vanA gene. MLST analysis revealed 9 sequence types (STs), which belonged to a single clonal complex (CC78, clonal lineage C1). Five strains showing incongruence between phenotype and genotype (VanB-vanA) did not belong to the same genotypic clone. The esp gene was detected in all VREF strains, showing 12 different esp repeat profiles. Data suggest that an epidemic clonal group of VREF, CC78 with esp gene, is also present in Asia and has differentiated into multiple diverse genotypic clones during the evolutionary process.Since the first isolation of vancomycin-resistant Enterococcus faecalis and Enterococcus faecium in 1988 (17), vancomycinresistant enterococci (VRE) have become one of the major threats to public health in many parts of the world. Although E. faecalis is more common in human infections, vancomycin resistance is more frequently observed in E. faecium isolates. Most vancomycin-resistant E. faecium (VREF) strains isolated in Korea showed the VanA phenotype, which is defined as having high-level resistance to vancomycin and teicoplanin (2). VREF isolates with the VanB phenotype characterized by variable levels of resistance to vancomycin but by susceptibility to teicoplanin have been reported in Korea since 1997 (12). Generally, the vanA gene cluster confers the VanA phenotype and vanB gene cluster is associated with the VanB phenotype. Recently, however, VRE strains with the vanA gene and VanB phenotype have been found in Japan, Taiwan, and Korea (3,6,8,11).VREF is an important concern not only because VREF infection is difficult to treat in clinical practice but also because VREF clones can spread within hospitals as well as between regions or countries. Molecular epidemiologic studies could clarify the genetic relatedness and molecular evolution of VREF clones. In the current study, we have investigated the phenotypic and genotypic characteristics of VREF isolates from four tertiary-care hospitals in Korea by using the broth microdilution test, pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and analysis of the esp repeat profile.
MATERIALS AND METHODS
VREF isolates.A total of 98 vancomycin-resistant E. faecium (VREF) isolates from four tertiary-care hospitals in Korea (Samsung Medical Center, Severans Hospital, Kyunghee University Hospital, and Kyungbuk National University Hospital) were analyzed in this study. The most common specimen source was urine (25 isolates) followed by rectal swab (14 isolates), blood (13 isolates), pus (9 isolates), wound (5 isolates), fluid (5 isolates), sputum (2 isolates), and tissue (2 isolates). Duplicate strains f...
