title: Loss of vancomycin resistance not completely dependent on the Tn1546 element in Enterococcus faecium isolates.
abstract: We investigated characteristics of 3 Enterococcus faecium strains (SHY-1, SHY-2, and SHY-3) isolated successively from 1 patient. In vitro susceptibility testing was performed using broth microdilution method. Change of vancomycin MIC was monitored during incubation with vancomycin for SHY-3 strain. Genetic backgrounds were determined both by multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE). In addition, the genetic variations among Tn1546 element were investigated by polymerase chain reaction (PCR) assay and sequencing. vanA and vanX expression of 3 strains was evaluated using quantitative real-time (qRT)-PCR method. Although all the strains possessed the vanA gene, SHY-3 was susceptible to glycopeptides, while SHY-1 and SHY-2 were resistant to glycopeptides. Judged by MLST and PFGE, 3 strains have the same genetic background. The vancomycin resistance of SHY-3 was not recovered after exposure to vancomycin. The vanA and vanX genes were expressed in strains SHY-1 and SHY-2 but not in strain SHY-3, although the SHY-2 and SHY-3 strains shared the same arrangement of the van gene cluster, a common 88-bp deletion in vanS gene. Our results indicate that vancomycin resistance might not be completely dependent on the Tn1546 element.
authors.affiliation: Department of Molecular Cell Biology, Sungkyunkwan University School of Medicine, Suwon, South Korea.
authors.forename: Hyun Jin
authors.initials: HJ
authors.lastname: Choi
authors.forename: Daesil
authors.initials: D
authors.lastname: Nam
authors.forename: Kyong Ran
authors.initials: KR
authors.lastname: Peck
authors.forename: Jae-Hoon
authors.initials: JH
authors.lastname: Song
authors.forename: Dongwoo
authors.initials: D
authors.lastname: Shin
authors.forename: Kwan Soo
authors.initials: KS
authors.lastname: Ko
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis; D019729:Carbon-Oxygen Ligases / Q000096:biosynthesis; D002648:Child; D004251:DNA Transposable Elements; D016521:Electrophoresis, Gel, Pulsed-Field; D016984:Enterococcus faecium / Q000145:classification / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D005260:Female; D020869:Gene Expression Profiling; D005838:Genotype; D006801:Humans; D058885:Multilocus Sequence Typing; D020133:Reverse Transcriptase Polymerase Chain Reaction; D046929:Serine-Type D-Ala-D-Ala Carboxypeptidase / Q000096:biosynthesis; D020713:Vancomycin Resistance
chemical_list: D001426:Bacterial Proteins; D004251:DNA Transposable Elements; C071437:VanA ligase, Bacteria; D046929:Serine-Type D-Ala-D-Ala Carboxypeptidase; C091956:VanX dipeptidase; D019729:Carbon-Oxygen Ligases