Which nuclear characteristic is associated with Entamoeba coli?

• A. No peripheral chromatin; large karyosome
• B. Coarse, uneven peripheral chromatin; large eccentric karyosome
• C. Fine, even peripheral chromatin; small central karyosome
• D. No peripheral chromatin; irregular clump of four to eight chromatin granules

Answer: (B)

Distinguishing Entamoeba coli relies on its nuclear appearance in stained forms. Entamoeba coli shows coarse, uneven chromatin lining the edge of the nucleus, with a relatively large karyosome that is displaced toward the periphery (eccentric). This gives the nucleus an irregular, off-center mass of chromatin. In contrast, Entamoeba histolytica has fine, evenly distributed peripheral chromatin and a small, centrally located karyosome. The cyst form of E. coli often has up to eight nuclei, whereas E. histolytica cysts typically have four. Therefore, the pattern of coarse, uneven peripheral chromatin with a large eccentric karyosome is characteristic of Entamoeba coli.