title: ArmA methyltransferase in a monophasic Salmonella enterica isolate from food.
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.
authors.affiliation: ANSES, Laboratoire de Sécurité des Aliments, Maisons-Alfort, France.
authors.forename: Sophie A
authors.initials: SA
authors.lastname: Granier
authors.forename: Laura
authors.initials: L
authors.lastname: Hidalgo
authors.forename: Alvaro
authors.initials: A
authors.lastname: San Millan
authors.forename: Jose Antonio
authors.initials: JA
authors.lastname: Escudero
authors.forename: Belen
authors.initials: B
authors.lastname: Gutierrez
authors.forename: Anne
authors.initials: A
authors.lastname: Brisabois
authors.forename: Bruno
authors.initials: B
authors.lastname: Gonzalez-Zorn
mesh_terms: D000617:Aminoglycosides / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D024881:Drug Resistance, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D005516:Food Microbiology; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D019779:Salmonella enterica / Q000187:drug effects / Q000201:enzymology*
chemical_list: D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D008780:Methyltransferases