Emergence of an IncIγ plasmid encoding CMY-2 ß-lactamase associated with the international ST19 OXA-30-producing ß-lactamase Salmonella Typhimurium multidrug-resistant clone.

OBJECTIVES: To analyse the genetic environment of the bla(CMY-2) gene in a multidrug-resistant isolate belonging to the OXA-30-producing Salmonella enterica serotype Typhimurium clone widespread in European countries.
METHODS: Preliminary characterization of CMY-2 was performed after determining the phenotype against β-lactams, the pI (isoelectric focusing) and the presence of bla genes (PCR). The genetic context of the bla(CMY-2) gene was identified by PCR mapping and further sequencing. Plasmid analysis included determination of transferability, size and content (S1-PFGE/hybridization), and characterization of the incompatibility group (PCR-based replicon typing, hybridization and sequencing).
RESULTS: The ΔISEcp1-bla(CMY-2)-blc-sugE cassette identified is located in the pndC-trbA region of an IncIγ conjugative plasmid designated pSTHV23035. This plasmid differs from previously described European IncI plasmids coding for CMY in the IncI replicon type and in the integration site of the element carrying bla(CMY-2).
CONCLUSIONS: The emergence of bla(CMY-2) located in a new IncIγ plasmid in an isolate belonging to the international widespread multidrug-resistant sequence type (ST) 19 OXA-30-producing Salmonella Typhimurium clone is reported for the first time. Acquisition of a new bla(CMY-2)-IncIγ plasmid by Salmonella multidrug-resistant strains is of concern since these plasmids diminish the activity of therapeutically important broad-spectrum β-lactams and contribute to the persistence and pathogenicity of widespread clones.