2. Entamoeba
coli
• Entamoeba coli is a non-
pathogenic species of Entamoeba
that frequently exists as a
commensal parasite in the human
gastrointestinal tract. E. coli is
important in medicine because it
can be confused during
microscopic examination of stained
stool specimens with the
pathogenic Entamoeba histolytica.
3. Trophozoites
• Measure between 18 to 27μm.
• Some trophozoites may be as small as 12μm,
whereas others may be as large as 55μm.
• Equipped with blunt pseudopods.
• Exhibits sluggish, nonprogressive motility.
4. Cysts
• Vary in size from 8 to 35μm and average of 12 to
25μm.
• Thick cell wall surrounds the round to spherical
cyst.
• One to eight nuclei with the typical nuclear
features may be seen in unstained as well as as
stained preparations.
5.
6. Life Cycle
• Cysts are typically found in formed stool,
whereas trophozoites are typically found
in diarrheal stool. Intestinal colonization
with nonpathogenic amebae occurs after
ingestion of mature cysts in fecally
contaminated food, water, or fomites.
• Excystation occurs in the small intestine
• and trophozoites are released, which
migrate to the large intestine. The
trophozoites multiply by binary fission
and produce cysts, and both stages are
passed in the feces
