Occurrence of class 2 integrons among multi-drug resistant Shigella sonnei isolated from Tehran, Iran in 2005

Shigellosis is one of the major causes of morbidity in children with diarrhea in Iran. Integrons play an important role in the evolution and dissemination of multidrug resistance in gram-negative bacteria. The occurrence of integrons among Shigella spp. is frequently reported throughout the world. The aim of this study was to assess the occurrence of class 2 integrons among the multi drug resistant S. sonnei isolated from Iranian children in 2005. The study was conducted in two major pediatric hospitals in Tehran, Iran. Fecal specimens and rectal swab collected from patients were cultured and identified as Shigella by the conventional methods. Antimicrobial susceptibility test was performed according to the standard CLSI guideline. Multi-drug resistant isolates of S. sonnei were further examined for the presence of class 2 integron by PCR using specific primers. Amplicons were confirmed by restriction endonuclease analysis. A total of 83 multi-drug resistant S. sonnei strains were isolated. Of these, 45 (54%) exhibited a class 2 integron of 2.1 kbp, and 34 (41%) a class 2 integron of 1.3 kbp. Class 2 integrons were not detected in four isolates. The results showed an increased occurrence of class 2 integron carrying S. sonnei isolated from children in Tehran in 2005.