Differences Between Entamoeba histolytica and Entamoeba coli

Genus Entamoeba includes a group of amoebic parasites. Among them Entamoeba histolytica is an important human pathogen causing amoebic dysentery as well as hepatic amoebiasis. Entamoeba coli is a commensal of large intestine, but doesn’t invade tissues.
Definitive diagnosis of amoebiasis depends on the demonstration of E. histolytica trophozoite or cyst in stool. Cases might get misdiagnosed because of similarities in their structure. Following are the structural differences between E. histolytica and E. coli.


S.N Characteristics Entamoeba histolytica Entamoeba coli

Trophozoite

1. Structure Entamoeba-histolytica-trophozoite Entamoeba-coli-trophozoite
2. Size 12-30 µm 20-40 µm
3. Motility Progressive.

Hyaline, fingerlike pseudopodia

Sluggish, nondirectional

Granular pseudopodia

4. Nucleus 1, difficult to visualize in unstained smear 1, often visible in unstained smear
5. Karyosome Sharp central Eccenteric
6. Pheripheral Chromatin Fine and dispersed Coarse and Clumped
7. Cytoplasmic Inclusions RBCs, leukocytes and tissue debris but no bacteria Bacteria and other material but never RBCs

Cysts

1. Structure Entamoeba-histolytica-cyst Entamoeba-coli-cyst
2. Size 10-15 µm 15-25 µm
3. Shape Usually spherical Usually spherical, may be oval, triangular or other shaped
4. Nucleus Mature Cyst=4 nuclei Mature Cyst=8 Nuclei
5. Peripheral Chromatin Fine and dispersed Coarsely granular or clumped
6. Chromatoid Bodies Rounded ends Filamentous, thread like, pointed ends
7. Glycogen Mass Visible in uninucleate stage Large and visible in binucleate stage
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Dhurba Giri is the founder and author of LaboratoryTests.org. He is a Medical Laboratory Technologist and Scientific Blogger from Pokhara, Nepal. Connect with him:

6 Comments

  1. Very nice drawings. One question. I think I learned that the number of nuclei for E. histolytica cysts was four or less and for E. coli it was more than four. I know for cysts in transition there maybe some exceptions, but for mature cysts am I wrong?

    • Hello Tod,
      The early cyst contains single nucleus. In case of E. histolytica, as the cyst matures, the nucleus undergoes two successive mitotic divisions to form two and then four nuclei. The mature cyst is quadrinucleate. Hence number of nucleus varies from one to four. It varies from one to eight in case of E. coli, and mature cyst contains eight.

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