Parasitology Artifacts - Entamoeba coli morphology

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Entamoeba coli

The ability to identify amoeba based on nuclear structure in iodine wet mount preparations is limited. Cysts of the amoeba are usually granular. Cysts of the mature pathogenic E. histolytica contain four nuclei while those of the non-pathogenic E. coli contain up to eight nuclei.
		The single nucleus of the trophozoite is often visible in unstained preparations with the non-compact karyosome that is eccentrically located.

Sometimes the nuclei may contain a central karyosome with uniform, peripheral chromatin and may be confused with the pathogenic Entamoeba histolytica, as in the E. coli at left.

A distorted Giardia cyst is also evident in this field.

Immature E. coli cysts containing four or fewer of the eight nuclei may be difficult to distinguish from E. histolytica.

But not so in these wet preparations where 5-7 nuclei can be seen.

Sometimes uninucleate cysts can also be seen with a large central glycogen vacuole pushing the nucleus to the margin of the cyst. Note the eccentrically placed karyosome.

A dark Giardia cyst is also evident in this phase mount.

E.coli trophozoite
Trichrome stain x 1000

These two trophozoites demonstrate some typical features of the parasite.

karyosomes are eccentrically positioned
perpheral chromatin is irregularly distributed
cytoplasm is vacuolated

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