Detection of Quinolone Resistance Pattern and Presence of qnr Genes in Human Salmonella Isolates at Mymensingh, Bangladesh.

Among the quinolones, fluoroquinolones are broad spectrum antimicrobial agents used for treating many clinical infections including Salmonellosis. Although high level of resistance to fluoroquinolones remains low in Salmonella but reduced susceptibility is increasing worldwide. Plasmid-mediated quinolone resistance (PMQR) of qnr type (qnrA, B and S) has been identified now a day in several enterobacterial species including Salmonella spp. This cross-sectional study was held at department of Microbiology, Mymensingh Medical College, Mymensingh, Bangladesh from March 2019 to February 2020. This study was conducted to determine the current quinolone resistance pattern and to detect the presence of qnrA, qnrB and qnrS genes among Salmonella isolates. Antimicrobial susceptibility test of 36 Salmonella isolates were done by disc diffusion method. MIC of ciprofloxacin was detected by agar dilution method. Then amplification with specific primers of qnrA, qnrB and qnrS genes were performed for all Salmonella isolates. The present study observed 80.5% resistance to nalidixic acid, 33.3% to ciprofloxacin and 19.4% to ofloxacin by disc diffusion method. qnr A gene was detected in 2(5.5%) isolates, where as qnrS was detected in 5 (13.8%) isolates. None of the isolates was positive for qnrB gene. All the qnrA positive isolates showed resistance to Ciprofloxacin (MIC=128μg/ml) and Ofloxacin. In conclusion, presence of qnr genes in the study isolates is alarming, because, rapid dissemination might occur due to conjugative plasmid mediated horizontal transfer.