Prevalence of Plasmid-Mediated Quinolone Resistance Genes among Extended-Spectrumβ-Lactamase-ProducingKlebsiella pneumoniaeHuman Isolates in Iran

Abstract

The purpose of this study was to determine the prevalence and molecular characterization of plasmid-mediated quinolone resistance (PMQR) genes (qnrA, qnrB, qnrS, aac(6′)-Ib-cr, andqepA) among ESBL-producingKlebsiella pneumoniaeisolates in Kashan, Iran. A total of 185K. pneumoniaeisolates were tested for quinolone resistance and ESBL-producing using the disk diffusion method and double disk synergy (DDST) confirmatory test. ESBL-producing strains were further evaluated for theblaCTX-Mgenes. The PCR method was used to show presence of plasmid-mediated quinolone resistance genes and the purified PCR products were sequenced. Eighty-seven ESBL-producing strains were identified by DDST confirmatory test and majority (70, 80.5%) of which carriedblaCTX-Mgenes including CTX-M-1 (60%), CTX-M-2 (42.9%), and CTX-M-9 (34.3%). Seventy-seven ESBL-producingK. pneumoniaeisolates harbored PMQR genes, which mostly consisted ofaac(6′)-Ib-cr(70.1%) andqnrB(46.0%), followed byqnrS(5.7%). Among the 77 PMQR-positive isolates, 27 (35.1%) and 1 (1.3%) carried 2 and 3 different PMQR genes, respectively. However,qnrAandqepAwere not found in any isolate. Our results highlight high ESBL occurrence with CTX-M type and high frequency of plasmid-mediated quinolone resistance genes among ESBL-producingK. pneumoniaeisolates in Kashan.