Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 15 5 2023 10 11 625 630 Nabi Jomehzadeh Department of Microbiology, School of Medicine, Abadan University of Medical Sciences, Abadan, Iran Khadijeh Ahmadi Department of Microbiology, School of Medicine, Abadan University of Medical Sciences, Abadan, Iran Nazanin Ataee Department of Biology, Kavian Institute of Higher Education, Mashhad, Iran Maryam Afzali Department of Microbiology, Faculty of Medicine, Mashhad Medical Sciences, Islamic Azad University, Mashhad, Iran; Department of Laboratory Sciences, Faculty of Paramedicine, Mashhad Medical Sciences, Islamic Azad University, Mashhad, Iran 2023 02 05 2023 04 24 Background and Objectives: An increase in the antibiotic resistance of Shigella isolates has caused major global challenges in antimicrobial therapy. Knowledge of local antibiotic resistance trends is essential for selecting appropriate antibiotic treatment regimens. This study aimed to evaluate the frequency of efflux-mediated tetracycline resistance (tet) and plasmid-mediated quinolone resistance (qnr) genes among Shigella isolates. Materials and Methods: This survey investigated 91 Shigella isolates, obtained from children with acute diarrhea. The isolates were identified using standard biochemical tests and confirmed by polymerase chain reaction (PCR) assay. Besides, the susceptibility of isolates to six selected antibiotics was assessed by the disk diffusion method. All tetracycline-resistant and nalidixic acid and ciprofloxacin resistant strains were screened for tet and qnr genes by a multiplex PCR assay. Results: According to the results of antibiotic susceptibility tests, the highest level of antibiotic resistance was related to tetracycline (80.2%) and doxycycline (78.1%), respectively. All isolates were sensitive to tigecycline. The PCR results showed that 40.6%, 3.1%, 21.8%, 61.6% and 28.7% of the isolates carried qnrA, qnrB, qnrS, tetA, and tetB genes, respectively. None of the isolates contained tetC and tetD genes. Conclusion: The current findings revealed that tetA and qnrA genes might play a key role in conferring tetracycline and quinolone resistance. https://ijm.tums.ac.ir/index.php/ijm/article/view/4115 https://ijm.tums.ac.ir/index.php/ijm/article/download/4115/1608