ArmA methyltransferase in a monophasic Salmonella enterica isolate from food

Antimicrob Agents Chemother. 2011 Nov;55(11):5262-6. doi: 10.1128/AAC.00308-11. Epub 2011 Aug 22.

Abstract

The 16S rRNA methyltransferase ArmA is a worldwide emerging determinant that confers high-level resistance to most clinically relevant aminoglycosides. We report here the identification and characterization of a multidrug-resistant Salmonella enterica subspecies I.4,12:i:- isolate recovered from chicken meat sampled in a supermarket on February 2009 in La Reunion, a French island in the Indian Ocean. Susceptibility testing showed an unusually high-level resistance to gentamicin, as well as to ampicillin, expanded-spectrum cephalosporins and amoxicillin-clavulanate. Molecular analysis of the 16S rRNA methyltransferases revealed presence of the armA gene, together with bla(TEM-1), bla(CMY-2), and bla(CTX-M-3). All of these genes could be transferred en bloc through conjugation into Escherichia coli at a frequency of 10(-5) CFU/donor. Replicon typing and S1 pulsed-field gel electrophoresis revealed that the armA gene was borne on an ~150-kb broad-host-range IncP plasmid, pB1010. To elucidate how armA had integrated in pB1010, a PCR mapping strategy was developed for Tn1548, the genetic platform for armA. The gene was embedded in a Tn1548-like structure, albeit with a deletion of the macrolide resistance genes, and an IS26 was inserted within the mel gene. To our knowledge, this is the first report of ArmA methyltransferase in food, showing a novel route of transmission for this resistance determinant. Further surveillance in food-borne bacteria will be crucial to determine the role of food in the spread of 16S rRNA methyltransferase genes worldwide.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aminoglycosides / pharmacology
  • Anti-Bacterial Agents / pharmacology
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Drug Resistance, Bacterial / genetics
  • Escherichia coli / drug effects
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Food Microbiology*
  • Methyltransferases / genetics
  • Methyltransferases / metabolism*
  • Molecular Sequence Data
  • Salmonella enterica / drug effects
  • Salmonella enterica / enzymology*

Substances

  • Aminoglycosides
  • Anti-Bacterial Agents
  • Bacterial Proteins
  • Methyltransferases

Associated data

  • GENBANK/HQ728525