Non-Pathogenic Amoeba
Several species of protozoans may be mistaken for Entamoeba histolytica.  Care must be taken to correctly identify the infection so that the correct treatment can be administered or other infectious agents sought after.
 
Entamoeba dispar morphologically identical to E. histolytica.  It must be separated by isoenzymatic, immunologic or molecular analyses. 
Entamoeba hartmanni  some consider this a separate species.  It differs from E. histolytica by being smaller in size.
Entamoeba coli distinguished from E. histolytica by having an eccentric endosome, and mature cysts with 8 nuclei.  If chromatoidal bodies are present, they have splintered ends, rather than rounded as in E. histolytica.
Endolimax nana this is a very small amoeba (6-15um) with a large, eccentric endosome and thin nuclear envelope.  Mature cysts contain 4 nuclei.
Iodamoeba butschlii both the trophozoite and cyst have one nucleus with a large endosome.  The cyst contains a large glycogen vacuole that stains darkly with iodine.

Images of Non-pathogenic amoeba species:
 

Entamoeba coli trophozoite
Entamoeba coli cyst
E. coli trophozoite:  Note the eccentric endosome in the nucleus (centric in E. histolytica). E. coli cyst:  Note the number of nuclei - 5 clearly visible in this focal plane compared to only 4 in E. histolytica.
Endolimax nana trophozoite
Endolimax nana cyst
Endolimax nana trophozoite:  Note the large endsome and thin layer of pigment around the nucleus. Endolimax nana cyst:  Contains 4 nuclei (3 seen in this focal plane) with large endosomes.
Iodamoeba buetschlii cyst
Iodamoeba buetschlii cyst
Iodamoeba buetschlii cyst:  Note the large endosome in the nucleus and the large glycogen vacuole. Iodamoeba buetschlii cyst:  Note the large endosome in the nucleus and the large glycogen vacuole.

 
Return to the Entamoeba histolytica Pathology Page
1999 - All rights reserved.  Produced by Brian E. Keas.