Clonal Lineage Analysis of Shigella flexneri Isolates Circulating in Ahvaz, Iran

Background: Shigellosis is a significant public health challenge particularly in developing countries, and the spread of antibiotic resistance genes through integron structures has become an important problem in the treatment of Shigellosis. The aim of this study was to investigate the genetic association of Shigella flexneri antibiotic resistant clones collected from Ahvaz between 2013 and 2015 by pulse field gel electrophoresis (PFGE) method. Methods: A total of 45 S. flexneri isolates, which were resistant to ampicillin and cotrimoxazole, were obtained from patients with Shigellosis referred to Ahvaz hospitals during 2013 - 2015. PCR was performed to evaluate the frequency of Sul1, int1, blaOXA, and int2 genes. In addition, pulse field gel electrophoresis method was used to investigate the genetic relationship between 40 S. flexneri isolates. Results: PCR results showed that the highest frequency was related to the sul1 gene with 80 (36 isolates) and the lowest frequency was related to class 2 integron with 15.5 (7 isolates); 31.11 (14 isolates) of the isolates were sul1 and int1. Also, 13.33 (6 isolates) had blaOXA and int1 genes, simultaneously. But none of the isolates had class 1 integrons and class 2 integrons at the same time. PFGE results showed 25 different pulsotype patterns, of which 16 isolates had their own unique pattern and were divided into 16 pulsotypes, and 27 isolates were divided into 9 pulsotypes. Conclusions: int2 and sul1 resistance genes had an upward trend from 2013 to 2015 and the results of PFGE indicated a different origin of S. flexneri clones