E. Coli is a non-pathogenic amoeba that frequently exists as a commensal parasite in the human intestines. E. coli is important in medicine because it can be confused with E. Histolytica during microscopic examination of stool samples.
Within the human intestine, the parasite is a trophozoite, or feeding stage parasite. The parasite forms resistant cysts which are passed in the feces. If these cysts are ingested (i.e. by consuming contaminated food or water), the cysts release trophozoites once they reach the intestine.