Shigella species

Shigella was first discovered in 1896 by a Japanese microbiologist, Kiyoshi Shiga, who was investigating an outbreak of sekiri (means “dysentery” in Japanese). He isolated a bacillus from stool sample and called it Bacillus dysenteriae, now it is known as Shigella dysenteriae type 1. The toxin produced by this organism is called, Shiga toxin. Shigella are a member of the Enterobacteriaceae family and causes shigellosis characterized by bacillary dysentery (mucoid bloody stool). Shigella are commonly found in water contaminated with human feces and fecal-oral route is the primary mode of transmission. It is responsible for a worldwide health problem; however, it is a serious concern in the developing countries. It is estimated that Shigella spp. account for 1.1 million deaths and 165 million cases of dysentery annually worldwide. Shigellosis has a high morbidity and mortality rate in children under 5 years of age. Malnourished children are highly susceptible and Shigella infection further promotes impaired nutrition, recurring infection and retarded growth. Antibiotic resistant strains are continuously emerging thus treatment regiments become very difficult against shigellosis. CDC estimates annually there are 18,000 reported cases of shigellosis in the US. Since the disease sometimes appears as mild and not reported, thus the number could be as high as 360,000 cases per year.