Entamoeba hartmanni

Entamoeba hartmanni is an ameba that is generally considered nonpathogenic.

Disease / Pathogenesis

Entamoeba hartmanni is not known to cause disease in humans.

Location in the Host

Entamoeba hartmanni is located in the lumen of the colon and cecum.

Geographic Distribution

Entamoeba hartmanni is found worldwide.

Live Cycle

Entamoeba hartmanni are transmitted by the ingestion of cyst in contaminated water or food.

Image courtesy of CDC

Morphology & Diagnosis

Entamoeba hartmanni are very small ameba with the cyst forms ranging between 5-10u. They are spherical with mature cysts having 4 nuclei while immature cysts will have 1-2. The nuclei will have karyosomes that are small, compact and discreet.

Trophozoites are 5-12u in size and are usually nonprogressive with bacterial inclusions present in the cytoplasm. The central karyosome is very small and compact, usually eccentrically located.


Entamoeba hartmanni in trichrome stain preparation (100X oil immersion) – note the small central karyosome. Organism size 11u..

Entamoeba hartmanni in trichrome stain ( 100X high dry magnification ) – Note the small size (10u) and small pinpoint karyosome – photo by W. Vientos