Antimicrobial susceptibility and virulence gene analysis of species causing dysentery in Iranian children: Implications for fluroquinolone resistance.

species significantly impact global health due to their role in diarrheal diseases. A 2019-2022 cross-sectional study on 432 stool samples from pediatric patients in Mashhad, Iran, identified spp. and tested their susceptibility to 12 antimicrobials by the disk diffusion method. The presence of virulence factors, namely , , , and , as well as plasmid-mediated quinolone resistance (PMQR) genes, including , , , , and , were ascertained through the utilization of polymerase chain reaction techniques. Sequencing of 15 isolates detected mutations within quinolone resistance-determining regions (QRDRs) at the and genes, indicating fluoroquinolone (FQ) resistance. 19.2 % (83/432) of stool samples contained , primarily (77.1 %), followed by (21.6 %) and (1.2 %). Most isolates were from children under five (55.4 %). All strains had the gene, lacked and , and 86.7 % had . High resistance was noted for ampicillin and tetracycline (84.3 % each), trimethoprim-sulfamethoxazole (81.9 %), and azithromycin (60.2 %). 87.1 % of isolates were multidrug-resistant (MDR). The most common PMQR genes were and (41 % each). The gene, prevalent in 36.1 % of cases, is reported in Iran for the first time. The most common PMQR profile was (15.7 %). Resistance to nalidixic acid and ciprofloxacin was 45.8 % and 12 %, respectively. The isolates exhibited mutations in the (at codons 83, 87, and 211) and (at codons 80, 84, 93, 126, 128, 129, and 132) genes. The D87Y mutation in the gene was the most common in isolates, occurring in 73 % of cases. The F93S and L132T mutations in the gene were unique to this study. Empirical FQ therapy in patients infected with MDR , possessing PMQR determinants and/or mutations in the QRDRs of and , may escalate the risks of secondary diseases, extended treatment duration, therapeutic failure, and resistance spread. Consequently, the necessity for continuous surveillance and genetic testing to detect FQ-resistant strains is of paramount importance.