Parasitology Diagnostic Laboratory

Entamoeba coli

The two images below are cysts of non-pathogenic Entamoeba coli. The trophozoites of these amoebae vary in size from 15-50 µm (range 20-25 µm). They typically have a single nucleus containing a large diffuse karyosome and irregular peripheral chromatin. The cytoplasm is generally granular and vacuolated. The first of these E. coli cysts is a trichrome-stained fixed specimen, whereas the second is an iodine-stained wet mount. Cysts measure between 10-35 µm (range 15-25 µm ). Unlike Entamoeba histolytica, the mature cyst of E. coli has 8 nuclei, and contains chromatin bars with pointed ends. Infection occurs by ingesting contaminated food or water.