Prevalence of Silent Plasmid-Mediated Quinolone Resistance (PMQR) Genes Among Clinical Isolates Fluoroquinolone-Sensitive Klebsiella pneumoniae

Plasmid-mediated quinolone resistance (PMQR) genes confer varying degrees of fluoroquinolone (FQ) resistance. Silent antibiotic resistance genes are DNA sequences typically not expressed, spread among strains through horizontal gene transfer, and could be active due to gene transfer. This study aimed to detect silent PMQR genes among FQs-sensitive K. pneumoniae isolated from clinical samples in Duhok province, Iraq. Standard microbiological methods were performed to identify K. pneumoniae, and then these bacteria were confirmed by species-specific genes. Samples were subjected to an antimicrobial susceptibility test by the Kirby-Bauer disc diffusion technique, then detection of targeted PMQR genes was done by the conventional polymerase chain reaction (PCR) method. Out of, 120 K. pneumoniae, 32 FQs-sensitive K. pneumoniae isolates were subjected for the molecular study; 53.1% of isolates (17/32) harbored silent PMQR genes, and among harbored PMQR genes, the frequency of genes was 12/17 (70.6%), 6/17 (35.3%), 5/7 (29.4%), 4/17 (23.5%) for, qnrA, qnrB, qnrS, and aac (6′)-Ib- cr respectively, in addition, 9/17 (53%) of isolates harbored more than one gene of PMQR genes. Furthermore, the qnrA gene had the highest percentage of PMQR genes, while the qepA gene was not detected. The dissemination of silent PMQR genes could offer a future risk for public health under the selective pressure of an antibiotic for a long time or transfer to other bacteria and then become active genes.