An AFLP-based database of Shigella flexneri and Shigella sonnei isolates and its use for the identification of untypable Shigella strains

Genetic characteristics and changing antimicrobial resistance among Shigella spp. isolated from hospitalized diarrhoeal patients in Kolkata, India

To study the prevalence pattern and trends in the phenotypic and genetic characteristics of shigellae, we tested 212 isolates isolated from diarrhoeal patients admitted to the Infectious Diseases Hospital, Kolkata, India, from November 2007 to October 2010. Prevalence of Shigella spp. was higher in the >5 years age group (69 %) than in children in the <5 years age group (31 %). Serotypes 2a, 3a and untypable isolates of Shigella flexneri were frequently detected. An increase in the isolation of Shigella sonnei (15 %) is a novel trend in this region. Fluoroquinolone resistance among S. flexneri serotypes 2a, 3a and other serogroups of shigellae is another evolving trend. The set gene was exclusively present in S. flexneri 2a, and the sen gene was detected in all serogroups. PFGE revealed the grouping of S. flexneri isolates according to their serotypes with approximately 80-100 % similarity, whilst Shigella dysenteriae type 2 and S. sonnei were clonal in nature. There was no demarcation in the prevalence of serotypes, antimicrobial resistance or clonality between the two age groups.