Entamoeba gingivalis (Gros, 1849) Brumpt(1913)
There is no known cyst stage for Entamoeba gingivalis; trophozoites (the active stage) live in the oral cavity of humans, residing in the gingival pockets near the base of the teeth. They feed on bacteria and other debris. Like some related species found in the large intestines of humans (Entamoeba coli, Ent. hartmanni, Ent. polecki, Endomilax nana, and Iodamoeba buetschlii), they are not considered pathogenic. Trophozoites are transmitted person-to-person orally by kissing or via fomites (such as eating utensils). The trophozoite stage of Ent. gingivalis is morphologically similar to that of Ent. histolytica and the two should be differentiated, as both can be coughed up in sputum specimens (for the latter, when present in pulmonary abscesses). Entamoeba gingivalis has a worldwide distribution.