title: Association of the novel aminoglycoside resistance determinant RmtF with NDM carbapenemase in Enterobacteriaceae isolated in India and the UK.
abstract: OBJECTIVE
  16S rRNA methyltransferases are an emerging mechanism conferring high-level resistance to clinically relevant aminoglycosides and have been associated with important mechanisms such as NDM-1. We sought genes encoding these enzymes in isolates highly resistant (MIC >200 mg/L) to gentamicin and amikacin from an Indian hospital and we additionally screened for the novel RmtF enzyme in 132 UK isolates containing NDM.
  
  
  METHODS
  All highly aminoglycoside-resistant isolates were screened for armA and rmtA-E by PCR, with cloning experiments performed for isolates negative for these genes. Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry was used to determine the methylation target of the novel RmtF methyltransferase. RmtF-bearing strains were characterized further, including susceptibility testing, PFGE, electroporation, PCR-based replicon typing and multilocus sequence typing of rmtF-bearing plasmids.
  
  
  RESULTS
  High-level aminoglycoside resistance was detected in 140/1000 (14%) consecutive isolates of Enterobacteriaceae from India. ArmA, RmtB and RmtC were identified among 46%, 20% and 27% of these isolates, respectively. The novel rmtF gene was detected in 34 aminoglycoside-resistant isolates (overall prevalence 3.4%), most (59%) of which also possessed a bla(NDM) gene; rmtF was detected in 6 NDM producers from the UK. It was found on different plasmid backbones. Four and two isolates showed resistance to tigecycline and colistin, respectively.
  
  
  CONCLUSIONS
  RmtF was often found in association with NDM in members of the Enterobacteriaceae and on diverse plasmids. It is of clinical concern that the RmtF- and NDM-positive strains identified here show additional resistance to tigecycline and colistin, current drugs of last resort for the treatment of serious bacterial infections.
authors.affiliation: Department of Animal Health and VISAVET, Universidad Complutense de Madrid, Madrid, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Hidalgo
authors.forename: Katie L
authors.initials: KL
authors.lastname: Hopkins
authors.forename: Belen
authors.initials: B
authors.lastname: Gutierrez
authors.forename: Cristina M
authors.initials: CM
authors.lastname: Ovejero
authors.forename: Suruchi
authors.initials: S
authors.lastname: Shukla
authors.forename: Stephen
authors.initials: S
authors.lastname: Douthwaite
authors.forename: Kashi N
authors.initials: KN
authors.lastname: Prasad
authors.forename: Neil
authors.initials: N
authors.lastname: Woodford
authors.forename: Bruno
authors.initials: B
authors.lastname: Gonzalez-Zorn
mesh_terms: D000583:Amikacin / Q000494:pharmacology; D000617:Aminoglycosides / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics*; D015780:Carbapenems / Q000494:pharmacology*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial; D004755:Enterobacteriaceae / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics* / Q000302:isolation & purification; D004756:Enterobacteriaceae Infections / Q000382:microbiology; D005839:Gentamicins / Q000494:pharmacology; D006801:Humans; D007194:India; D008780:Methyltransferases / Q000235:genetics*; D008969:Molecular Sequence Data; D010957:Plasmids; D017422:Sequence Analysis, DNA; D006113:United Kingdom; D001618:beta-Lactamases / Q000235:genetics*
chemical_list: D000617:Aminoglycosides; D001426:Bacterial Proteins; D015780:Carbapenems; D004269:DNA, Bacterial; D005839:Gentamicins; D000583:Amikacin; D008780:Methyltransferases; C035181:rRNA (adenosine-O-2'-)methyltransferase; D001618:beta-Lactamases; C063912:carbapenemase
keywords: 16S rRNA methyltransferases; antimicrobial; resistance