Characterization of multidrug-resistant, qnrB2-positive and xtended-spectrum-β-lactamase-producing Salmonella Concord and Salmonella Senftenberg isolates

Abstract

Objectives: To characterize plasmids and resistance genes of multidrug-resistant (MDR) Salmonella Senftenberg and Salmonella Concord isolated from patients in the Netherlands. Methods: The resistance genes of four MDR Salmonella isolates (three Salmonella Concord and one Salmonella Senftenberg) were identified by miniaturized microarray, PCR and sequencing. Plasmids were characterized by S1 nuclease-PFGE and PCR-based replicon typing (PBRT). Linkage between plasmids and genes was determined by conjugation experiments and microarray analysis. The genetic relationship between the three Salmonella Concord isolates was determined by XbaI-PFGE. Results: A large variety of resistance genes was detected, including qnrB2 and the -lactamase genes blaTEM-1 and blaSHV-12 in all isolates; moreover all Salmonella Concord isolates also harboured blaCTX-M15. Salmonella Senftenberg harboured a large IncHI2 plasmid. The three Salmonella Concord isolates harboured two large plasmids typed as IncHI2 and IncA/C. Conclusions: We detected the first plasmid-mediated MDR Salmonella isolates in the Netherlands harbouring both qnr and extended-spectrum -lactamase (ESBL) genes. In Salmonella Senftenberg one large plasmid (IncHI2) and in Salmonella Concord two large plasmids (IncHI2 and IncA/C) were responsible for the multidrug resistance. © The Author 2010. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved.