Annals of Clinical Microbiology, The official Journal of the Korean Society of Clinical Microbiology


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Epidemiology and Molecular Characterization of Vancomycin-Resistant Enterococcus faecalis

Original article

Annals of Clinical Microbiology (Ann Clin Microbiol) 2015 September, Volume 18, Issue 3, pages 76-81.

Epidemiology and Molecular Characterization of Vancomycin-Resistant Enterococcus faecalis

Joon Kim1, Kyung Ho Choi2, Young Sun Kim2, Wee Gyo Lee2
1Department of Biomedical Sciences, The Graduate School, Ajou University, 2Department of Laboratory Medicine, Ajou University College of Medicine, Suwon, Korea


Background: Vancomycin-resistant Enterococci (VRE) infections are caused by Enterococcus faecium in about 90% of the cases but can also be caused by Enterococcus faecalis. Thus, this study investigates factors that cause a low isolation rate of vancomycin-resistant E. faecalis (VREfs). To this end, the authors study the clinical traits, resistant gene structure, genomic classification, and molecular characteristics of the virulent factor.

Methods: From January 2001 through September 2011, 17 vanA-containing E. faecalis isolates were collected from hospitalized patients at Ajou University Hospital in Korea. Identification, antimicrobial susceptibility testing, and PCR of van and esp genes were performed. Pulsed-field gel electrophoresis (PFGE) was used for strain typing. PCR and sequencing of the internal regions of Tn1546 were performed for structural analysis of the van gene.

Results: Of 4,235 VRE infections, 3,918 (92.5%) were caused by E. faecium, and 95 (2.2%) were caused by E. faecalis. In 67% of VREfs infections, there was a preceding occurrence of E. faecium infection. All isolates were of genotype vanA. Our isolates were divided into three types according to the distribution of IS elements integrated into Tn1546 (types I to IIb). The PFGE results showed no clonal relatedness among isolates.

Conclusion: Our study found that VREfs infections affect patients who have experienced vancomycin-resistant E. faecium. (VREfm) infection or undergo invasive procedures. The VREfs seems to involve the horizontal transfer of Tn1546 transposon from VREfm. (Ann Clin Microbiol 2015;18:76-81)


IS1216V, IS1542, Tn1546, Vancomycin- resistant Enterococcus faecalis