Table 5.

Current taxonomy and nomenclature of the genus Shigella. Habitat and pathogenicity of species^a.

Species	Main serotypes	Habitat and pathogenicity
Shigella dysenteriae	15 serotypes.	Intestinal pathogens of humans and primates, causing bacillary dysentery.
Shigella flexneri	8 serotypes 9 subserotypes	Humans are the primary reservoir. A long-term carrier state occurs in few cases.
Shigella boydii	19 serotypes	Shigella dysenteriae serotype 1 causes more severe disease then other serotypes and produces a potent exotoxin (Shiga toxin). Large epidemics in developing countries are commonly caused by serotype 1. Diseases caused by other serotypes may be mild or severe.
Shigella sonnei	1 serotype	Shigella sonnei illness is usually milder than that caused by other Shigella species.

^aAdapted from [34]. Nomenclature according to [9].