Plasmid-mediated 16S rRNA methylases conferring high-level aminoglycoside resistance in Escherichia coli and Klebsiella pneumoniae isolates from two Taiwanese hospitals

J Antimicrob Chemother. 2004 Dec;54(6):1007-12. doi: 10.1093/jac/dkh455. Epub 2004 Oct 14.


Objectives: This study was conducted to investigate the occurrence of 16S rRNA methylases that confer high-level aminoglycoside resistance in Klebsiella pneumoniae and Escherichia coli isolates from two Taiwanese hospitals and the characteristics of these isolates.

Methods: A total of 1624 K. pneumoniae and 2559 E. coli isolates consecutively collected over an 18 month period from a university hospital and seven E. coli and eight K. pneumoniae isolates that were resistant to amikacin from a district hospital were analysed. Two 16S rRNA methylase genes, armA and rmtB, were detected by PCR-based assays. beta-Lactamase characteristics were determined by phenotypic and genotypic methods.

Results: Overall, 28 armA-positive and seven rmtB-positive isolates were identified, and extended-spectrum beta-lactamases (ESBLs) were detected in 33 (94.3%) isolates. The prevalence rates of armA and rmtB at the university hospital were 0.9% (n=15) and 0.3% (n=5) in K. pneumoniae and 0.4% (n=10) and 0.04% (n=1) in E. coli. CTX-M-3, CTX-M-14, SHV-5-like ESBLs, and CMY-2 were detected alone or in combination in 21, 6, 11, and 2, respectively, of the 28 armA-positive isolates. CTX-M-14 was detected in six of the seven rmtB-positive isolates. Fingerprinting of conjugative plasmids revealed the dissemination of closely related plasmids containing both armA and bla(CTX-M-3). PFGE suggests that armA and rmtB spread by both horizontal transfer and clonal spread.

Conclusions: This is the first report of the emergence of 16S rRNA methylases in Enterobacteriaceae in Taiwan. The spread of the multidrug-resistant isolates producing both ESBLs and 16S rRNA methylases may become a clinical problem.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amikacin / pharmacology
  • Aminoglycosides / pharmacology*
  • Anti-Bacterial Agents / pharmacology*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Conjugation, Genetic
  • Electrophoresis, Gel, Pulsed-Field
  • Escherichia coli / drug effects*
  • Escherichia coli / enzymology
  • Escherichia coli / genetics
  • Hospitals
  • Humans
  • Klebsiella pneumoniae / drug effects*
  • Klebsiella pneumoniae / enzymology
  • Klebsiella pneumoniae / genetics
  • Methyltransferases / genetics*
  • Microbial Sensitivity Tests
  • Plasmids / genetics*
  • Taiwan
  • beta-Lactamases / genetics
  • beta-Lactamases / metabolism


  • Aminoglycosides
  • Anti-Bacterial Agents
  • Bacterial Proteins
  • Amikacin
  • Methyltransferases
  • 16S rRNA (adenine(1518)-N(6)-adenine(1519)-N(6))-dimethyltransferase
  • beta-Lactamases