Entamoeba gingivalis is a non-pathogenic ameba that inhabits the human oral cavity and occasionally other sites. Although it is often found in conjunction with periodontal disease, no causative association has been definitively identified.
There is no known cyst stage for Entamoeba gingivalis; trophozoites live in the oral cavity of humans, residing in the gingival pockets near the base of the teeth. They are not considered pathogenic, and feed on bacteria and other debris. Trophozoites are transmitted person-to-person orally by kissing or fomites (such as eating utensils) . The trophozoite stage of E. gingivalis is morphologically similar to that of E. histolytica. The two should be differentiated, as both can be coughed up in sputum specimens (if E. histolytica is present in pulmonary abscesses).
E. gingivalis is a cosmopolitan species and is very common globally.
E. gingivalis is common in individuals with poor oral hygiene or periodontal disease. However, several studies have not definitely demonstrated any causative correlation. It appears that diseased periodontal tissue and associated Actinomyces bacteria simply provide a favorable environment for the ameba to develop. Occasionally, E. gingivalis trophozoites have also been reported from the female genital tract, particularly in association with use of an intrauterine device (IUD).
E. gingivalis trophozoites stained with trichrome.
There is no known cyst stage for Entamoeba gingivalis; trophozoites measure 10-20 µm. Trophozoites possess a single nucleus that contains a small, centrally-located karyosome and fine peripheral chromatin. The cytoplasm often contains ingested leukocytes, bacteria and other debris, very rarely red blood cells. The trophozoites may also extend agranular pseudopodia while the main cell cytoplasm remains granular in appearance. Living specimens can move quickly.
Identification of E. gingivalis is usually made by the finding of trophozoites in scrapings of the gums and teeth; trophozoites may be seen ingesting white cells and epithelial cell nuclei. Two genetic sub types exist, the ST1 and ST2-kamaktli subtypes, though any clinical significance or morphologic differences between these two have not been investigated at the time of writing. E. gingivalis may be found in sputum on rare occasions or detected in cervical Pap smears. As such, it is important to differentiate them from the morphologically-similar trophozoites of E. histolytica, which may be found in sputum from pulmonary abscesses and invading the female genital tract.
Standard precautions apply for the processing of sputum samples.
Bradbury, R.S., Roy, S., Ali, I.K., Morrison, J.R., Waldner, D., Hebbeln, K., Aldous, W., Jepson, R., Delavan, H.R., Ndubuisi, M. and Bishop, H.S., 2019. Case Report: Cervicovaginal Co-Colonization with Entamoeba gingivalis and Entamoeba polecki in Association with an Intrauterine Device. The American Journal of Tropical Medicine and Hygiene, 100 (2), pp.311-313.
Garcia, G., Ramos, F., Maldonado, J., Fernandez, A., Yáñez, J., Hernandez, L. and Gaytán, P., 2018. Prevalence of two Entamoeba gingivalis ST1 and ST2-kamaktli subtypes in the human oral cavity under various conditions. Parasitology Research 117 (9), pp.2941-2948.
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