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

Abstract

Objectives: To analyse the genetic environment of the blaCMY-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 b-lactams, the pI (isoelectric focusing) and the presence of bla genes (PCR). The genetic context of the blaCMY-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 DISEcp1-blaCMY-2-blc-sugE cassette identified is located in the pndC-trbA region of an IncIg 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 blaCMY-2. Conclusions: The emergence of blaCMY-2 located in a new IncIg 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 blaCMY-2-IncIg plasmid by Salmonella multidrugresistant strains is of concern since these plasmids diminish the activity of therapeutically important broadspectrum b-lactams and contribute to the persistence and pathogenicity of widespread clones.