Intestinal Protozoa

Intestinal Protozoa
Amoeba: Entamoeba histolytica
Diseases: Entamoeba histolytica causes amebic dysentery and liver abscess.
Important Properties: The life cycle has two stages:
the motile (trophozoite) the nonmotile (cyst)
is found within the intestinal and extraintestinal lesions and in diarrheal stools. found in nondiarrheal stools.

--------------- These cysts are killed by boiling but not by chlorination of water supplies. They are removed by filtration of water.
The mature trophozoite has a single nucleus with lining of peripheral chromatin and a central nucleolus (karyosome). The cyst has four nuclei, an important diagnostic criterion
Pathogenesis & Epidemiology:
1. The organism is acquired by ingestion of cysts that are transmitted by the fecal–oral route in contaminated food and water. Anal–oral transmission, e.g., among male homosexuals.
2. The ingested cysts differentiate into trophozoites in the ileum but tend to colonize the cecum and colon.
3.The trophozoites invade the colonic epithelium and secrete enzymes that cause localized necrosis. As the lesion reaches the muscularis layer, a typical "flask-shaped" ulcer forms.