title: Comparison of vanA gene mRNA levels between vancomycin-resistant Enterococci presenting the VanA or VanB phenotype with identical Tn1546-like elements.
abstract: OBJECTIVE
  During the routine screening of vancomycin-resistant Enterococci faecium (VREfm) we found that VanA phenotype-vanA genotype and VanB phenotype-vanA genotype isolates had an identical Tn1546-like element structure. This study aimed to evaluate the genetic background and vanA gene expression to identify the mechanisms of the development of the VanB phenotype-vanA genotype VREfm.
  
  
  METHODS
  Twelve VREfm isolates were collected from a 1500-bed tertiary-care teaching hospital in Beijing. Genetic variations of the Tn1546-like element were determined by an overlapping polymerase chain reaction assay and sequencing. The genetic background was determined by pulsed-field gel electrophoresis and mutilocus sequence typing. vanA gene expression was evaluated using a TaqMan quantitative real-time polymerase chain reaction.
  
  
  RESULTS
  For the 12 isolates, six isolates with the VanA phenotype-vanA genotype and six with the VanB phenotype-vanA genotype were identified. According to the structure analysis of the Tn1546-like elements, our isolates were divided into two types. In the four isolates of type A, IS1542 and IS1216V were inserted into the orf2-vanR and vanX-vanY regions, respectively. In the eight isolates of type D, a similar insertion as type A occurred, except for an ISEfa4 insertion into IS1542. A significant difference in vanA gene expression was observed between the VanA and VanB phenotype isolates in type A, but not in type D. Mutilocus sequence typing and pulsed-field gel electrophoresis analysis showed that these isolates have a different genetic background.
  
  
  CONCLUSIONS
  Our results indicated that the occurrence of the VanB phenotype-vanA genotype might not completely depend on the structure of Tn1546-like elements and vanA gene expression.
authors.affiliation: Department of Infectious Diseases and Clinical Microbiology, Beijing Chao-Yang Hospital, Capital Medical University, Beijing, People's Republic of China.
authors.forename: Hong
authors.initials: H
authors.lastname: Shen
authors.affiliation: Department of Infectious Diseases and Clinical Microbiology, Beijing Chao-Yang Hospital, Capital Medical University, Beijing, People's Republic of China.
authors.forename: Yingmei
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Infectious Diseases and Clinical Microbiology, Beijing Chao-Yang Hospital, Capital Medical University, Beijing, People's Republic of China.
authors.forename: Jiuxin
authors.initials: J
authors.lastname: Qu
authors.affiliation: Department of Infectious Diseases and Clinical Microbiology, Beijing Chao-Yang Hospital, Capital Medical University, Beijing, People's Republic of China. Electronic address: caobin_ben@yahoo.com.
authors.forename: Bin
authors.initials: B
authors.lastname: Cao
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics*; D019729:Carbon-Oxygen Ligases / Q000235:genetics*; D002681:China; D016521:Electrophoresis, Gel, Pulsed-Field; D016984:Enterococcus faecium / Q000187:drug effects / Q000235:genetics; D014644:Genetic Variation / Q000235:genetics; D006801:Humans; D008826:Microbial Sensitivity Tests; D058885:Multilocus Sequence Typing; D060888:Real-Time Polymerase Chain Reaction; D062606:Tertiary Care Centers; D019895:Transposases / Q000235:genetics*; D014640:Vancomycin / Q000494:pharmacology; D020713:Vancomycin Resistance / Q000235:genetics*; D065507:Vancomycin-Resistant Enterococci / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; C071437:VanA ligase, Bacteria; C079913:VanB protein, Enterococcus; D014640:Vancomycin; D019895:Transposases; D019729:Carbon-Oxygen Ligases
keywords: Enterococci faecium; Tn1546-like elements; teicoplanin; vancomycin resistance