title: Multiplication of blaOXA-23 is common in clinical Acinetobacter baumannii, but does not enhance carbapenem resistance.
abstract: To investigate the copy number of blaOXA-23and its correlation with carbapenem resistance in carbapenem-resistant Acinetobacter baumannii (CRAB).
  
  
  
  A total of 113 blaOXA-23-positive clinical CRAB isolates were collected from two hospitals in Zhejiang province, China. Their genetic relatedness was determined by MLST. The MIC of imipenem was determined using the agar diffusion method and the copy number of blaOXA-23was measured using quantitative real-time PCR (qRT-PCR). The complete genomes of five clinical CRAB strains were sequenced using PacBio technology to investigate the multiplication mechanism of blaOXA-23.
  
  
  
  Most of the isolates (100/113) belonged to global clone II and the MIC of imipenem ranged from 16 to 96 mg/L. The gene blaOXA-23resided exclusively in Tn2006 or Tn2009. Approximately 38% of the isolates carried two or more copies of blaOXA-23. The copy number of blaOXA-23was not correlated with the MIC of imipenem. Within the five sequenced strains, multiple copies of blaOXA-23were either tandemly clustered or independently inserted at different genomic sites.
  
  
  
  Multiplication of blaOXA-23is common in CRAB, but does not enhance carbapenem resistance. Multiplication can be present in the form of either tandem amplifications or independent insertions at different sites.
authors: Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China.
authors: Xiaoting
authors: X
authors: Hua
authors: Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China.|Institute of Translational Medicine, Zhejiang University School of Medicine, Hangzhou, China.
authors: Jianfeng
authors: J
authors: Shu
authors: Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China.
authors: Zhi
authors: Z
authors: Ruan
authors: Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China.
authors: Yunsong
authors: Y
authors: Yu
authors: Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China pandafengye@zju.edu.cn.|Institute of Translational Medicine, Zhejiang University School of Medicine, Hangzhou, China.
authors: Ye
authors: Y
authors: Feng
mesh_terms: D040981:Acinetobacter baumannii / Q000145:classification / Q000187:drug effects* / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics*; D015780:Carbapenems / Q000494:pharmacology*; D002681:China; D004251:DNA Transposable Elements; D018628:Gene Dosage; D005838:Genotype; D006761:Hospitals; D006801:Humans; D008826:Microbial Sensitivity Tests; D060888:Real-Time Polymerase Chain Reaction; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D015780:Carbapenems; D004251:DNA Transposable Elements; D001618:beta-Lactamases; C000599728:beta-lactamase OXA-23, Acinetobacter baumannii