Characterization of Shigella flexneri Isolates by Tandem Repeat Analysis and Pulsed-Field Gel Electrophoresis

Pulsed-field gel electrophoresis (PFGE) is highly discriminatory molecular typing tools for many bacterial pathogens and Multilocus variable-number tandem repeat (VNTR) analysis (MLVA) is prominent typing tool which has been developed for a variety of bacterial pathogens. Knowledge on molecular characterization and typing of Shigella strains of any geographical region is important for epidemiology, pathogenesis and treatment of shigellosis and as VNTRs appear to contain greater diversity, hence, analysis of these regions will provide greater discrimination among the strains of identical serotypes. In this report, we identified 8 repeat sequence loci in the genomic sequences of the Shigella flexneri 2a strains 301 and 2457T. Seven tandem repeats were found to be variable after testing a set of 40 multidrugresistant clinical isolates of S.flexneri, which were isolated from children with acute diarrhea and attending to the outpatient department of Dr. B. C. Roy Memorial Hospital for Children, Kolkata, India between 2000 and 2005. Seven VNTR loci were found to be the powerful markers for strain differentiation and phylogenetic studies of S.flexneri. This study would provide a new insight and impetus for further investigations on global epidemiology of Shigella isolates.