Molecular analysis of integrons and antimicrobial resistance profile in Shigella spp. isolated from acute pediatric diarrhea patients

Introduction: Shigella spp. is a growing global health concern due to increasing multiple drug resistance, commonly resulting in therapeutic failure. Integrons are gene expression systems run by integrase genes. The aims of this study were detection of class I, II and III integrons and assessment of antimicrobial resistance in Shigella spp. isolated from acute pediatric diarrhea patients. Materials and methods: From January to December 2015, 16 Shigella spp. were isolated from 310 non-duplicative diarrheal stool samples in Children’s Medical Center, Tehran, Iran. The isolates were analyzed for their antibiotic susceptibility using CLSI guidelines M100-S14. Multiplex PCR was used for amplification of I, II and III integron-associated integrase (intl) genes. Results: Of 310 stool samples, 16 (5.2%) were positive for Shigella spp., in 7 of them S. sonnei and in 9 of them S. flexneri were identified. Results of the antimicrobial susceptibility test showed that 6.2%, 50%, 31.2%, 6.2%, 81.2%, 56.2% and 31.2% of the isolates were resistant to gentamicin, chloramphenicol, nalidixic acid, ciprofloxacin, tetracycline, ampicillin and trimethoprim-sulfamethoxazole, respectively. Multiplex PCR results revealed that 6.2% (1/16), 31.2% (5/16), 50% (8/16) of Shigella isolates carried intlI, intlII and both intlI/intllI genes. No class 3 integrons were detected. Discussion: In this study, multidrug resistance was seen in Shigella isolates similar to that in isolates from other geographical areas. This is possible due to inappropriate use of antimicrobials. Furthermore, prevalence of multidrug resistance was significantly linked to the presence of integrin genes. Conclusion: A class 2 integron plays a role in presence of multidrug resistance in Shigella spp. It is vital to prevent the spread of antibiotic resistance through continuous monitoring.