Virulence gene profiles of Shigella species isolated from stool specimens in India: its association with clinical manifestation and antimicrobial resistance.

Shigella is the major cause of bacillary dysentery worldwide, especially in developing countries. There are several virulence factors essential for the organism to be virulent which are generally present in the virulence plasmid and on chromosomal pathogenicity islands. The present study was undertaken to determine the virulence gene profile of Shigella spp isolated from a clinical specimen and to study their significant association with common clinical symptoms and antimicrobial resistance. Sixty Shigella whole genome sequences, including 22 S. flexneri, 14 S. sonnei, 17 S. boydii and 7 S. dysenteriae were analyzed for the presence of virulence genes. The gene found predominantly in this study were ipaH (90%) followed by sigA (83%), and lpfA (78%) respectively. The virulence genes were significantly higher in S. flexneri, particularly in serotype 2 compared to S. sonnei. Interestingly, a significant association was observed between sigA gene and fever whereas sepA and sigA were found to be associated with diarrhea. Among the studied Shigella isolates, the presence of virulence genes was found higher in isolates resistant to more than three antibiotic classes. The present work revealed the varying incidence of virulence determinants among different Shigella serogroups and shows their contribution to disease severity.