Investigation of plasmid mediated quinolone resistance genes in quinolone-resistant Acinetobacter baumannii isolates

Objectives: To specifically assess the prevalence and transferability of PMQR genes in quinolone-resistant A. baumannii clinical isolates collected between September 2021 and December 2022 in Kırşehir, Turkey, using molecular techniques and conjugation assays. Methods: Twenty-nine non-duplicate quinolone-resistant A. baumannii isolates were analyzed. Identification and susceptibility were determined via VITEK® 2. PMQR genes (qnrA, qnrB, qnrC, qnrD, qnrS, qepA, oqxA, oqxB) and aac(6')-Ib-cr were detected by PCR. Conjugation experiments were performed using brothmating method to the transferability of PMQR genes. Results: In 29 A. baumannii isolates, qnrB, oqxA, aac(6')-Ib-cr, qnrS and oqxB genes were detected as 82.8%, 55.2%, 51.7%, 10.3% and 10.3%, respectively. No amplification was observed for qnrA, qnrC, qnrD, or qepA. Conjugation assay confirmed the horizontal transfer of the qnrB gene via a conjugative plasmid in one isolate and the conjugation transfer frequency was found to be 3.45%. Conclusion: Considering the increasing prevalence of multidrug-resistant A. baumannii in healthcare settings, the identification of transferable qnrB genes, even at a low frequency (3.45%), is clinically alarming, as it demonstrates the pathogen’s capacity to disseminate fluoroquinolone resistance horizontally. This underscores the urgent need for enhanced infection control policies, routine molecular surveillance of resistance genes, and strict antibiotic stewardship, especially in high-risk clinical units such as intensive care.