Association of Transferable Quinolone Resistance DeterminantqnrB19with Extended-Spectrumβ-Lactamases inSalmonellaGive andSalmonellaHeidelberg in Venezuela

Abstract

Four nontyphoidalSalmonellastrains with resistance to extended-spectrum cephalosporins and nonclassical quinolone resistance phenotype were studied. TwoS.Give were isolated from pediatric patients with acute gastroenteritis, and twoS.Heidelberg were recovered from raw chicken meat. Phenotypic characterization included antimicrobial susceptibility testing and detection of extended-spectrumβ-lactamases (ESBLs) by the double-disc synergy method. The detection of quinolone resistance-determining regions (QRDR) ofgyrA, gyrB, andgyrCgenes,blaESBLsgenes, and plasmid-mediated quinolone resistance (PMQR) determinants was carried out by molecular methods. Plasmid analysis included Southern blot and restriction patterns. Transferability of resistance genes was examined by transformation.blaTEM-1 + blaSHV-12genes were detected inS.Give SG9611 andblaTEM-1 + blaCTX-M-2in the other three strains:S.Give SG9811,S.Heidelberg SH7511, and SH7911. Regardless of origin and serovars, theqnrB19gene was detected in the 4 strains studied. All determinants of resistance were localized in plasmids and successfully transferred by transformation. This study highlights the circulation ofqnrB19associated withblaTEM-1,blaSHV-12, andblaCTX-M-2inS.Give andS.Heidelberg in Venezuela. The recognition of factors associated with increasing resistance and the study of the molecular mechanisms involved can lead to a more focused use of antimicrobial agents.