title: Mutations in DNA Gyrase and Topoisomerase IV in Ciprofloxacin-Nonsusceptible Extended-Spectrum -Lactamase-Producing Escherichia coli and Klebsiella pneumoniae.
abstract: BACKGROUND
  We investigated mutations in the quinolone resistance-determining region (QRDR) of ciprofloxacinnonsusceptible extended-spectrum -lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae by a statistical analysis.
  
  
  METHODS
  We collected 97 clinical isolates of ciprofloxacin-nonsusceptible ESBL-producing E. coli (55 strains) and K. pneumoniae (42 strains) from a tertiary-care university hospital in Seoul, Republic of Korea, between 2006 and 2008. The QRDR of the gyrA, gyrB, parC, and parE genes were amplified by PCR and sequenced.
  
  
  RESULTS
  Most E. coli isolates (53/55; 96.4%) with a minimum inhibitory concentration of ≥ 64 mg/L against ciprofloxacin had double mutations in gyrA (Ser-83Leu and Asp-87Asn) and at least one mutation in parC (Ser-80 Ile or Glu-84Val), with or without one in parE. Fifty E. coli (90.9%) isolates had a mutation in parE, of which Ile-529Leu (70.9%) was the most frequent. However, we could not find statistically significant variables in increasing ciprofloxacin resistance in E. coli isolates. Thirty-six K. pneumoniae isolates (36/42; 85.7%) had at least one mutation in gyrA, gyrB, or parC, and the mutation in gyrA might have been associated with plasmid-mediated quinolone-resistance (PMQR). Ser-80Ile in parC and aac(6')-Ib-cr in the K. pneumoniae isolates were significantly associated with an increased MIC of ciprofloxacin by ordinal logistic regression analysis.
  
  
  CONCLUSIONS
  The Ser-80Ile in parC and aac(6')-Ib-cr in K. pneumoniae are supposed to play an important role in increased ciprofloxacin resistance, but statistically significant variables could not be found in E. coli isolates in the present study.
authors.forename: Kyung Sun
authors.initials: KS
authors.lastname: Park
authors.forename: Hyung-Seok
authors.initials: HS
authors.lastname: Yang
authors.forename: You Sun
authors.initials: YS
authors.lastname: Nam
authors.forename: Hee Joo
authors.initials: HJ
authors.lastname: Lee
mesh_terms: D000900:Anti-Bacterial Agents; D002939:Ciprofloxacin; D027081:DNA Gyrase; D027101:DNA Topoisomerase IV; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli; D006801:Humans; D007711:Klebsiella pneumoniae; D008826:Microbial Sensitivity Tests; D009154:Mutation; D056910:Republic of Korea
chemical_list: D000900:Anti-Bacterial Agents; D002939:Ciprofloxacin; D027101:DNA Topoisomerase IV; D027081:DNA Gyrase