Genetic diversity of Shigella spp. and their integron content.

OBJECTIVES

The aim of this study was to investigate the occurrence and resistance gene content of class 1 and 2 integrons among Shigella spp. and to study the genetic diversity of isolates using the pulsed-field gel electrophoresis (PFGE) method.

METHODS AND

RESULTS

A total of 32 Shigella spp. were identified from 700 stool samples of patients with diarrhea from two provinces in Iran. S. sonnei (70.8%) and S. flexneri (62.5%) were the most frequent serogroups in Tehran and Razavi Khorasan provinces, respectively. Class 2 integrons were more frequent among Shigella spp. in comparison with class 1 integrons. Three different resistance gene arrays were identified among class 1 integrons. Dihydrofolate reductase (dfrA) gene cassette was detected in 78.9% of total integrons (class 1 and 2). PFGE analysis revealed clonal dissemination (62.5%) of a single clone with identical class 2 resistance gene content in Tehran province. Comparison of our Shigella pulsotypes with those published from other countries showed similar pulsotypes in India and Korea, with identical resistance profiles, which suggests dissemination of this (these) clone(s) in Asian countries.

CONCLUSIONS

Class 2 integrons were found to be predominant among our Shigella spp. This reflects the need to monitor the acquisition and dissemination of different resistant gene cassettes among integrons. Comparison of PFGE pattern through standard procedures promoted the molecular epidemiological surveys and identification of clonal isolates in Iran and other Asian countries.