Prevalence of Qnr determinants among bloodstream isolates of Escherichia coli and Klebsiella pneumoniae in a Taiwanese hospital, 1999-2005

J Antimicrob Chemother. 2008 Jun;61(6):1234-9. doi: 10.1093/jac/dkn111. Epub 2008 Mar 20.


Objectives: To determine the prevalence and characteristics of bloodstream isolates of Escherichia coli and Klebsiella pneumoniae with qnr genes in a Taiwanese hospital.

Methods: A total of 2035 E. coli and 1147 K. pneumoniae isolates collected between 1999 and 2005 were screened for qnrA, qnrB and qnrS by PCR and colony hybridization. Beta-lactamase genes, genetic relatedness and transferability were examined by PCR, PFGE and conjugation, respectively.

Results: The prevalence of qnr genes was 7.8% and 0.6% for K. pneumoniae and E. coli, respectively. The prevalence rates of qnrB2, qnrB4 and qnrS1 genes for K. pneumoniae were 2.3%, 3.6% and 2.8%, respectively, and for E. coli were 0.2%, 0% and 0.4%, respectively. The prevalence of qnrB4 in K. pneumoniae increased remarkably from 0% to 7.6% over the 7 study years. qnrA was not detected. Overall, the SHV-5-related, CTX-M-14, CTX-M-3, CMY-2, DHA-1 and IMP-8 beta-lactamases were detected alone or in combination in 82.0% of qnr-positive K. pneumoniae isolates and 41.7% of qnr-positive E. coli isolates. Notably, all qnrB4-positive isolates possessed the DHA-1 enzyme, and the majority of the qnrB2-positive isolates (E. coli, 100%; K. pneumoniae, 80.8%) produced SHV-5-related beta-lactamases. Genetic diversity was demonstrated by PFGE. Conjugation experiments revealed co-transfer of bla(SHV-12), bla(DHA-1) and bla(SHV-5) with qnrB2, qnrB4 and qnrS1, respectively.

Conclusions: qnr genes remained rare in E. coli but appeared to be increasing in K. pneumoniae in our hospital. Horizontal transfer may play a major role in the intra-hospital spread of qnr.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacteremia / microbiology*
  • Bacterial Proteins / genetics*
  • Conjugation, Genetic
  • Cross Infection / microbiology
  • DNA, Bacterial / genetics
  • Drug Resistance, Bacterial / genetics*
  • Electrophoresis, Gel, Pulsed-Field
  • Escherichia coli / genetics*
  • Escherichia coli / isolation & purification
  • Escherichia coli Infections / microbiology
  • Escherichia coli Proteins / genetics*
  • Hospitals
  • Humans
  • Isoelectric Focusing
  • Klebsiella Infections / microbiology
  • Klebsiella pneumoniae / genetics*
  • Klebsiella pneumoniae / isolation & purification
  • Microbial Sensitivity Tests
  • Taiwan
  • beta-Lactam Resistance / genetics
  • beta-Lactamases / classification
  • beta-Lactamases / genetics
  • beta-Lactamases / isolation & purification


  • Bacterial Proteins
  • DNA, Bacterial
  • Escherichia coli Proteins
  • Qnr protein, E coli
  • Qnr protein, Klebsiella pneumoniae
  • beta-Lactamases