Prevalence of Plasmid-Mediated Quinolone Resistance Genes among Extended-Spectrum β-Lactamase-Producing Klebsiella pneumoniae Human Isolates in Iran

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, and qepA) among ESBL-producing Klebsiella pneumoniae isolates in Kashan, Iran. A total of 185 K. pneumoniae isolates 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 the bla (CTX-M) genes. 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 carried bla (CTX-M) genes including CTX-M-1 (60%), CTX-M-2 (42.9%), and CTX-M-9 (34.3%). Seventy-seven ESBL-producing K. pneumoniae isolates harbored PMQR genes, which mostly consisted of aac(6′)-Ib-cr (70.1%) and qnrB (46.0%), followed by qnrS (5.7%). Among the 77 PMQR-positive isolates, 27 (35.1%) and 1 (1.3%) carried 2 and 3 different PMQR genes, respectively. However, qnrA and qepA were 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-producing K. pneumoniae isolates in Kashan.