Introduction
Shigella, which was first discovered in 1897, is a genus of Gram-negative, nonspore-forming, nonmotile, facultative aerobic, rod-shaped bacteria. It causes disease in primates, such as humans and gorillas, but not in other mammals. Shigella, closely related to E. coli, is one of the leading bacterial causes of diarrhea worldwide and causes moderate-to-severe diarrhea in African and South Asian children. Shigella species are classified by three serogroups and one serotype, including S. dysenteriae, S. flexneri, S. boydii and S. sonnei, of which S. flexneri is the most frequently isolated species worldwide, accounting for 60%.