Distribution of 16S rRNA Methylases Among Different Species of Gram-negative Bacilli With High-Level Resistance to Aminoglycosides

Eur J Clin Microbiol Infect Dis. 2010 Nov;29(11):1349-53. doi: 10.1007/s10096-010-1004-1. Epub 2010 Jul 8.


16S rRNA methylases confer high-level resistance to most aminoglycosides in Gram-negative bacteria. Seven 16S rRNA methylase genes, armA, rmtA, rmtB, rmtC, rmtD, rmtE and npmA, have been identified since 2003. We studied the distribution of methylase genes in more than 200 aminoglycoside-resistant Gram-negative clinical isolates collected in 2007 at our hospital in Shanghai, China. 16S rRNA methylase genes were amplified by polymerase chain reaction (PCR) among 217 consecutive clinical isolates of Gram-negative bacilli resistant to gentamicin and amikacin by a disk diffusion method. 16S rRNA methylase genes were present in 97.5% (193/198) of clinical isolates highly resistant to amikacin (≥512 μg/ml), with armA and rmtB detected in 67.2 and 30.3% of strains, respectively, while no 16S rRNA methylase genes were detected in 19 strains with amikacin minimum inhibitory concentration (MIC) ≤256 μg/ml. armA or rmtB genes were detected in 100% of 104 strains of Enterobacteriaceae, and these two genes were equally represented (49 vs. 55 strains). Genes for armA or rmtB were detected in 94.7% (89/94) of Acinetobacter baumannii and Pseudomonas aeruginosa strains, and armA was predominant (84 vs. 5 strains with rmtB). No rmtA, rmtC, rmtD or npmA genes were found. Enterobacterial repetitive intergenic consensus sequence (ERIC-PCR) indicated that armA and rmtB genes were spread by both horizontal transfer and clonal dissemination.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acinetobacter baumannii / drug effects
  • Acinetobacter baumannii / enzymology
  • Acinetobacter baumannii / genetics
  • Aminoglycosides / pharmacology*
  • Anti-Bacterial Agents / pharmacology
  • China
  • Drug Resistance, Bacterial / genetics*
  • Enterobacteriaceae / drug effects
  • Enterobacteriaceae / enzymology
  • Enterobacteriaceae / genetics
  • Gene Transfer, Horizontal
  • Gram-Negative Bacteria / drug effects*
  • Gram-Negative Bacteria / enzymology
  • Gram-Negative Bacteria / genetics*
  • Methyltransferases / genetics*
  • Methyltransferases / metabolism*
  • Microbial Sensitivity Tests
  • Polymerase Chain Reaction
  • Pseudomonas aeruginosa / drug effects
  • Pseudomonas aeruginosa / enzymology
  • Pseudomonas aeruginosa / genetics
  • RNA, Ribosomal, 16S* / metabolism


  • Aminoglycosides
  • Anti-Bacterial Agents
  • RNA, Ribosomal, 16S
  • Methyltransferases
  • rRNA (adenosine-O-2'-)methyltransferase