vanA-containing Enterococcus faecium susceptible to vancomycin and teicoplanin because of major nucleotide deletions in Tn1546
vanA-containing Enterococcus faecium susceptible to vancomycin and teicoplanin because of major nucleotide deletions in Tn1546
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DOI：
10.1093/jac/dkr379
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发表时间：
2011-12-01
影响因子：
5.2
通讯作者：
Roger, Michel
中科院分区：
文献类型：
--
作者：
Gagnon, Simon;Levesque, Simon;Roger, Michel
目的：在对万古霉素耐药的肠球菌(VRE)进行常规筛选的过程中，发现6株粪肠球菌经聚合酶链式反应(PCR)检测呈VANA阳性，而表型检测对万古霉素和替考拉宁敏感。本研究的目的是研究这些粪肠球菌Tn1546 vana基因簇的遗传组成。方法：对粪肠球菌进行抗生素敏感性、PFGE和Tn1546序列的结构分析。结果：对万古霉素敏感的vana阳性粪肠球菌存在3种PFGE图谱，缺失了参与抗性基因转录激活的vanR和vans基因。结论：临床标本中存在对万古霉素敏感的VANA阳性粪肠球菌，是Tn1546 VANA操纵子主要缺失的结果。我们的发现支持了VanR和Vans在肠球菌对万古霉素耐药表达中的重要作用。
Objectives: During the course of routine screening for vancomycin-resistant enterococci (VRE), we found six Enterococcus faecium isolates positive for vanA by PCR, but susceptible to vancomycin and teicoplanin by phenotypic testing. The aim of this study was to characterize the genetic composition of the Tn1546 vanA gene cluster of these isolates.Methods: The E. faecium isolates were characterized by antibiotic susceptibility, PFGE and structural analysis of the Tn1546 elements. Plasmids extracted from these isolates were used to determine the presence of the Tn1546 vanA gene cluster by PCR and the genomic organization of the deleted Tn1546 element by primer walking DNA sequencing.Results: The vancomycin-susceptible vanA-positive E. faecium isolates showed three PFGE patterns, and were missing the vanR and vanS genes that are responsible for the activation of transcription of resistance genes. Primer walking sequencing revealed that these genes were completely deleted and that interruptions in the vanA cluster were in the vicinity of insertion sequence elements.Conclusions: The presence of vancomycin-susceptible vanA-positive E. faecium in clinical samples results from major deletions in the Tn1546 vanA operon. Our findings support the essential role of vanR and vanS for the expression of resistance to vancomycin in enterococci.