title: Prevalence of the extended-spectrum beta-lactamase and qnr genes in clinical isolates of Escherichia coli.
abstract: BACKGROUND
  This study was performed to investigate the prevalence of qnr genes in clinical isolates of Escherichia coli from Korea that produce extended-spectrum beta-lactamases (ESBLs).
  
  
  METHODS
  During the period of May to June 2005, we collected clinical isolates of E. coli that were intermediate or resistant to ceftazidime and/or cefotaxime from 11 Korean hospitals. Antimicrobial susceptibility was determined by the disk diffusion and agar dilution methods. ESBL production was confirmed phenotypically by the double-disk synergy test. ESBL and qnr genes were searched for by PCR amplification, and the PCR products were then subjected to direct sequencing.
  
  
  RESULTS
  Double-disk synergy tests were positive in 84.3% (118/140) of ceftazidime- and/or cefotaxime-nonsusceptible E. coli isolates. The most prevalent types of ESBL in E. coli isolates were CTX-M-14 (N=41) and CTX-M-15 (N=58). Other ESBLs were also identified, including CTX-M-3 (N=7), CTX-M-9 (N=8), CTX-M-12 (N=1), CTX-M-57 (N=1), SHV-2a (N=2), SHV-12 (N=17) and TEM-52 (N=4). The qnrA1 and qnrB4 genes were identified in 4 and 7 ESBL-producing isolates, respectively.
  
  
  CONCLUSIONS
  CTX-M-type enzymes were the most common type of ESBL in E. coli isolates from Korea, and the qnr genes were not uncommon in ESBL-producing E. coli isolates. Dissemination of E. coli containing both ESBL and qnr genes could compromise the future usefulness of the expanded-spectrum antibiotics for the treatment of infections.
authors: Department of Laboratory Medicine and Research Institute of Bacterial Resistance, Yonsei University College of Medicine, Seodaemun-Gu, Seoul, Korea.
authors: Yongjung
authors: Y
authors: Park
authors: Hyun Kyung
authors: HK
authors: Kang
authors: Il Kwon
authors: IK
authors: Bae
authors: Juwon
authors: J
authors: Kim
authors: Jae Seok
authors: JS
authors: Kim
authors: Young
authors: Y
authors: Uh
authors: Seok Hoon
authors: SH
authors: Jeong
authors: Kyungwon
authors: K
authors: Lee
mesh_terms: D052978:Disk Diffusion Antimicrobial Tests; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D029968:Escherichia coli Proteins / Q000145:classification / Q000235:genetics*; D006801:Humans; D020128:Inhibitory Concentration 50; D016133:Polymerase Chain Reaction; D001618:beta-Lactamases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; C485384:Qnr protein, E coli; D001618:beta-Lactamases