title: Characterization of carbapenem-non-susceptible Escherichia coli isolates from a university hospital in Taiwan.
abstract: OBJECTIVE
  To investigate characteristics of nine carbapenem-non-susceptible (CP-NS) Escherichia coli isolates collected between 1999 and 2005 at a Taiwanese university hospital.
  
  
  METHODS
  Genetic relatedness was analysed by PFGE. beta-Lactamases were characterized by PCR and isoelectric focusing. Outer membrane proteins and transcripts were investigated by SDS-PAGE and northern blotting. Cloning experiments were performed to investigate the role of membrane permeability in carbapenem non-susceptibility.
  
  
  RESULTS
  The nine CP-NS isolates were found to produce the CMY-2 AmpC enzyme (n = 8), the CTX-M-14-type extended-spectrum beta-lactamase (ESBL) (n = 1), the SHV-12 ESBL (n = 1) and the IMP-8-type metallo-beta-lactamase (n = 1) alone or in combination. All CP-NS isolates revealed a decrease in the transcription and protein expression of ompC, and susceptibility to carbapenems was restored in one isolate by introducing the cloned ompC gene. PFGE revealed genetic diversity among the nine isolates. All patients with the CP-NS isolates had been treated with carbapenems (six patients) and/or extended-spectrum cephalosporins (five patients) before isolation.
  
  
  CONCLUSIONS
  Our study suggests that the decreased susceptibility to carbapenems in E. coli in the hospital might arise by the stepwise accumulations of multiple drug-resistance determinants in different clones.
authors.affiliation: Institute of Basic Medical Sciences, College of Medicine, National Cheng-Kung University, Tainan, Taiwan.
authors.forename: Yi-Fang
authors.initials: YF
authors.lastname: Liu
authors.forename: Jing-Jou
authors.initials: JJ
authors.lastname: Yan
authors.forename: Wen-Chien
authors.initials: WC
authors.lastname: Ko
authors.forename: Shu-Huei
authors.initials: SH
authors.lastname: Tsai
authors.forename: Jiunn-Jong
authors.initials: JJ
authors.lastname: Wu
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015780:Carbapenems / Q000494:pharmacology*; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics*; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology; D006785:Hospitals, University; D006801:Humans; D013624:Taiwan / Q000453:epidemiology
chemical_list: D000900:Anti-Bacterial Agents; D015780:Carbapenems