title: Characteristics of plasmid-mediated quinolone resistance genes in extended-spectrum cephalosporin-resistant isolates of Klebsiella pneumoniae and Escherichia coli in Korea.
abstract: BACKGROUND
  Quinolone resistance is frequently associated with extended-spectrum cephalosporin resistance in Enterobacteriaceae.
  
  
  METHODS
  The characteristics of plasmid-mediated quinolone resistance (PMQR) genes [qnr genes, aac(6')-Ib-cr and qepA] in clinical isolates of Klebsiella pneumoniae and Escherichia coli resistant to extended-spectrum cephalosporin were studied.
  
  
  RESULTS
  5 and 4 of 95 E. coli isolates but 46 (86/187) and 6% (12/187) of K. pneumoniae had qnr and aac(6')-Ib-cr, respectively, and 8 K. pneumoniae contained both genes.qepA was not identified. qnrB, especially qnrB4, was the predominant qnr subtype in K. pneumoniae [94 (88 qnrB of 94 qnr) and 88% (77 qnrB4 of 88 qnrB), respectively], and presence of qnrB4 was closely related with DHA-1 beta-lactamase (99%). However, K. pneumoniae isolates with qnrB4 and bla(DHA-1) were clonally diverse. beta-Lactamases produced by PMQR-containing isolates were variable: CMY-1, CTX-M-14, CTX-M-15, DHA-1, OXA type, SHV-2a, and SHV-12.
  
  
  CONCLUSIONS
  PMQR genes are widely distributed among clinical isolates of K. pneumoniae, and qnrB4 associated with bla(DHA-1) was the most common PMQR gene in Korea.
authors.affiliation: Division of Infectious Diseases, Medical College, Hanyang University, Seoul, South Korea.
authors.forename: Mi-Ran
authors.initials: MR
authors.lastname: Seo
authors.forename: Yoon Soo
authors.initials: YS
authors.lastname: Park
authors.forename: Hyunjoo
authors.initials: H
authors.lastname: Pai
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002511:Cephalosporins / Q000494:pharmacology*; D016000:Cluster Analysis; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D007711:Klebsiella pneumoniae / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D010957:Plasmids; D015363:Quinolones / Q000494:pharmacology*; D056910:Republic of Korea; D001618:beta-Lactamases / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D015363:Quinolones; D001618:beta-Lactamases