Molecular epidemiological characteristics of Shigella spp. isolated from river Narmada during 2005-2006

Shigellosis is an acute gastroenteritis caused by Shigella species. Forty isolates of Shigella spp. were obtained from the river Narmada during 2005-2006. Twenty-three isolates were identified as S. flexneri, 10 as S. sonnei, and seven as S. dysenteriae on the basis of biochemical tests and serotyping. All the isolates harbored at least one plasmid (range: 1-4) and exhibited 12 distinct plasmid profile patterns. Out of 40 isolates, 90% were found to be resistant against more than two antibiotics. All of the isolates were resistant to ciprofloxacin. It is noteworthy that all of the S. dysenteriae strains were resistant to chloramphenicol and trimethoprim, and that all of the S. flexneri and S. sonnei strains were resistant to cephotaxime, amikacin, and norfloxacin, which can be used for the treatment of shigellosis. Forty-two and a half percent of Shigella isolates were found to be Congo red positive. Since the Congo red binding test is cheap and simple, it can be used to determine the virulence properties of Shigella species. We could not find a specific correlation between serotype, antimicrobial resistance, and plasmid profile.