title: Identification of DHA-23, a novel plasmid-mediated and inducible AmpC beta-lactamase from Enterobacteriaceae in Northern Taiwan.
abstract: OBJECTIVE
  AmpC β-lactamases are classified as Amber Class C and Bush Group 1. AmpC β-lactamases can hydrolyze broad and extended-spectrum cephalosporins, and are not inhibited by β-lactamase inhibitors such as clavulanic acid. This study was conducted to identify DHA-23, a novel plasmid-mediated and inducible AmpC β-lactamase obtained from Enterobacteriaceae.
  
  
  METHODS
  A total of 210 carbapenem-resistant Enterobacteriaceae isolates were collected from a medical center (comprising two branches) in Northern Taiwan during 2009-2012. AmpC β-lactamase genes were analyzed through a polymerase chain reaction using plasmid DNA templates and gene sequencing. The genetic relationships of the isolates were typed using pulsed-field gel electrophoresis following the digestion of intact genomic DNA by using XbaI.
  
  
  RESULTS
  Three enterobacterial isolates (one Escherichia coli and two Klebsiella pneumoniae) were obtained from three hospitalized patients. All three isolates were resistant or intermediately susceptible to all β-lactams, and exhibited reduced susceptibility to carbapenems. These three isolates expressed a novel AmpC β-lactamase, designated DHA-23, approved by the curators of the Lahey website. DHA-23 differs from DHA-1 and DHA-6 by one amino acid substitution (Ser245Ala), exhibiting three amino acid changes compared with DHA-7 and DHA-Morganella morganii; three amino acid changes compared with DHA-3; four amino acid changes compared with DHA-5; and eight amino acid changes compared with DHA-2 (>97% identity). This AmpC β-lactamase is inducible using a system involving ampR.
  
  
  CONCLUSIONS
  This is the first report to address DHA-23, a novel AmpC β-lactamase. DHA-type β-lactamases are continuous threat in Taiwan.
authors.affiliation: Department of Laboratory Medicine, Taipei Medical University - Shuang Ho Hospital, New Taipei City Taiwan ; School of Medical Laboratory Science and Biotechnology, Taipei Medical University, Taipei Taiwan ; Graduate Institute of Biomedical Informatics, Taipei Medical University, Taipei Taiwan.
authors.forename: Wen-Shyang
authors.initials: WS
authors.lastname: Hsieh
authors.affiliation: Department of Medical Research, Mackay Memorial Hospital, New Taipei City Taiwan.
authors.forename: Nai-Yu
authors.initials: NY
authors.lastname: Wang
authors.affiliation: Department of Medical Research, Mackay Memorial Hospital, New Taipei City Taiwan.
authors.forename: Jou-An
authors.initials: JA
authors.lastname: Feng
authors.affiliation: Department of Medical Research, Mackay Memorial Hospital, New Taipei City Taiwan.
authors.forename: Li-Chuan
authors.initials: LC
authors.lastname: Weng
authors.affiliation: School of Medical Laboratory Science and Biotechnology, Taipei Medical University, Taipei Taiwan ; Department of Laboratory Medicine, Taipei Medical University Hospital, Taipei Taiwan.
authors.forename: Hsueh-Hsia
authors.initials: HH
authors.lastname: Wu
keywords: AmpC beta-lactamase; Enterobacteriaceae; antimicrobial resistance epidemiology