Detection of qnr resistance genes in Ciprofloxacin and Nalidixic acid resistant Salmonella spp. isolated from stool samples.

Gastroenteritis caused by Salmonella spp. and increasing of antibiotic resistance of this pathogen is of great concern for public health. This study was designed in order to detection plasmid-mediated quinolone resistance (PMQR) genes in Salmonella spp. isolated from stool and theirs correlation with Ciprofloxacin and Nalidixic acid resistance. A total of 40 Salmonella spp. isolates recovered from stool samples were examined for antimicrobial susceptibility and the presence of PMQR (qnrA, qnrB, qnrS) genes. Among all isolates, 30 (75%) were multidrug-resistant (MDR) and the majority of them proved to be resistant to Ampicillin, Cephalosporins, Nalidixic acid and Ciprofloxacin. 25 isolates (62.5%) harbored at least one qnr gene. Moreover, two or more PMQR genes coexisted in a 13 (32.5%) isolates. Antimicrobial susceptibility patterns of isolates revealed that 17 (42.5%) exhibited resistance to Nalidixic acid and 25 (62.5%) isolates to Ciprofloxacin. PCR assay detected that 22 of 40 (55%) Salmonella spp. carried the qnrS, 15 (37.5%) isolates harbored the qnrB, 11(27.5%) of them contained the qnrA. All the three qnrA, qnrB, qnrS genes were found in 10 (25%) isolates. The study demonstrated that the coexistence of PMQR genes among the Salmonella isolates increased the levels of resistance to quinolone antibiotics. Results of this study might improve understanding of the quinolone resistance of Salmonella spp.