53th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC), 2013, 02, C2-540─C2-540

Distribution of toxin-antitoxin systems for plasmid stability and plasmid replicon typing in vancomycin-resistant Enterococci from hospitals and poultry

Young-Hee Jung, Sung Young Lee, Yeong Seon Lee

Abstract

Background: It has been reported that resistance genes containing vanA is reserved and transferred by the toxin-antitoxin (TA) systems and replicon (rep) types of plasmids. Therefore, we investigated distribution of TA systems and rep genes, identified the size of plasmid and estimated plasmid stability in VRE isolates from hospital and poultry.
Methods: A total 200 VRE isolates, 135 clinical isolates (107 E. faecium and 28 E. faecalis) and 65 poultry E. faecium, were isolated from 2003 to 2012. Five TA systems and nine rep genes were detected using PCR. Plasmid size and position were identified by S1 nuclease PFGE and Southern hybridization. Plasmid stability in culture broth of Brain Heart Infusion was tested for 15 days.
Results: In TA systems, axe-txe was only detected in 85.0% clinical E. faecium isolates and ε-ζ were detected in 59.8% clinical E. faecium and 39.3% E. faecalis isolates and 90.8% poultry isolates, and par was only detected in 14.3% E. faecalis. axe-txe/ε-ζ were simultaneously detected in 57.9% clinical E. faecium isolates. In rep genes, pRE25 was identified in 42.9%, pAD1 in 28.6% and pIP501 in 10.7% of E. faecalis. In E. faecium, pLG1 was in 84.6% and pRE25 in 12.3% of poultry isolates and pRE25, pRUM and pLG1 were 71.0%, 68.2% and 67.3% in of clinical isolates, respectively. pRE25/pRUM/pLG1 was detected in 39.0% clinical E. faecium. Many of clinical E. faecium harbored two or more plasmids of 150~>200 kb, poultry E. faecium possessed one plasmid of 150~200 kb and E. faecalis had one plasmid of 50~100 kb. Resistance of vancomycin and erythromycin in VRE was stable as 80%~100% for fifteen days.
Conclusions: Distribution of TA systems and rep genes depended on species and samples sources. Clinical E. faecalis and poultry E. faecium carried only one TA system and rep type. However, in clinical E. faecium over two TA systems and rep genes were detected and plasmid size and number were more complicate and diverse than in E. faecalis and poultry E. faecium. Therefore, we expected that high VRE rate in clinical E. faecium would be resulted from these results.

• 본 연구는 질병관리본부 연구개발과제(과제번호 2012-N44003-00) 연구비를 지원받아 수행되었습니다.
• This research was supported by a fund(code 2012-N44003-00) by Research of Korea Centers for Disease Control and Prevention.