These are organisms that carry a toxin gene that has been acquired from a cousin of E. coli called Shigella. Shigella are always pathogenic. These organisms are common inhabitants of the intestinal tract of humans and animals. They can, however, also be found in soil, water, food or anything else that becomes contaminated with feces from these sources. The symptoms are those of an acute gastroenteritis that develops into a cramping, often grossly bloody diarrhea.
Fever is low-grade or absent.
Many cases are self-limiting, and resolve in eight to 10 days without specific treatment. A serious, sometimes fatal, complication may develop in some patients in which the kidneys become affected, presumably by the Shigella toxin, particularly in children. This is known as hemolytic uremic syndrome that can lead to kidney failure and sometimes an associated hemolytic anemia. Antibiotics, fluid and salt replacement, and bed rest are the usual treatment. Some physicians omit antibiotics but, depending on the patient, will do supportive care as warrants.