Entamoeba Gingivalis: Characteristics, Taxonomy, Morphology

Entamoeba gingivalis  is a commensal protozoan of the oral cavity that lives in gums, dental tartar, and tonsillar crypts. Some authors claim that it has been found outside the mouth, especially in vaginal and cervical smears from women with devices. It has also been seen in captive primates, horses, dogs, and cats.

This microorganism was discovered by G. Gros in 1849. At that time it was called Endamoeba gingivalis  and it was considered a commensal microorganism. TOAlthough this finding was observed in some patients suffering from periodontitis, there was no association of this pathology with the presence of the amoeba, a situation that lasted for more than a century.

In 1980 T. Lyons rescued interest in Entamoeba gingivalis, after he detected amoeboid microorganisms in periodontal pockets, and observed that these were absent in healthy sites.

Lyons suspected that the pathology could be related to the amoeba, so he implemented a treatment based on oxygen peroxide and metronidazole, with which he was successful.

However, this was not enough to classify E. gingivalis as a causative agent of periodontitis. There have been many studies on this in particular and there are still controversies about it.

characteristics

Entamoeba gingivalis is a non-invasive microorganism, as it does not spread outside its usual ecological niche.

There is a prevalence ranging from 6% to 80% of E. gingivalis in patients with oral affectations such as gingivitis, advanced periodontal disease, dental caries, abscesses or oral suppurations, dental prostheses and in biofilms formed at the base of the teeth.

However, it has also been found in patients with good oral health, but less frequently. Therefore, it has not been possible to define it as a pathogen, but perhaps it behaves more like an opportunist.

The normal microbiotas in living organisms are generally maintained without causing discomfort to the host as long as they are in perfect balance, but if for some reason one microorganism is exacerbated over others, there may be consequences.

Therefore, if the parasite proliferates more than normal, it could create an imbalance in the oral microbiota. This is how Entamoeba gingivalis can generate an inflammatory, degenerative and necrotic response in the gums and surrounding connective tissues, which promote microbial colonization in the periodontal pockets.

Although it is not the causal agent of the disease, it can contribute to its occurrence, acting together with bacteria. On the other hand, it has been speculated that the presence of some bacteria in the oral microbiota is favorable for reducing oral pathologies. For example,  Porphyromonas catoniae and Neisseria flavescens.

Therefore, they are considered passive indicators of oral health, but it is unknown whether their presence limits E. gingivalisWhat is known is that   Entamoebas gingivalis feeds on flaking cells at the edge of the gums, blood cells, and bacteria.

They also phagocytose the nuclei of polymorphonuclear cells, through a mechanism called exonucleophagy.

Taxonomy

Entamoeba gingivalis belongs to the Kingdom Protista , Phylum: Amoebozoa, Class: Archamoebae, Order: Mastigamoebida, Family: Entamoebidae, Genus: Entamoeba, Species: gingivalis.

Morphology

The trophozoite is unicellular in which a clear external ectoplasm and an internal granular endoplasm are distinguished. Only the vegetative or trophozoite form is known, measuring 5-35 µm.

Entamoeba gingivalis has a non-mobile stage, where the ectoplasm is barely visible, and a mobile phase where it appears as a thick layer that comprises approximately half the volume of the trophozoite.

It has a small central vesicular nucleus of 2 to 4 µm with a thin nuclear membrane , lined with fine chromatin granules grouped in the periphery. They contain a central or eccentric karyosome.

The endoplasm is granular and vacuolated. It is normally full of floating food particles.

Food vacuoles contain dark round bodies, derived largely from the nuclei of degenerated epithelial cells, lymphocytes, and occasionally leukocytes. E. gingivalis also ingests bacteria but to a lesser extent.

Basically E. gingivalis is a disintegrated cell killer.

The cytoplasm is finely granular and presents multidirectional ectoplasmic pseudopods that allow it to move.

It is unknown if it has the ability to encyst itself like other amoebas do.

Diagnosis or finding of the oral parasite

Entamoebas can be observed under the light microscope of samples taken from the ecological niches of the parasite. For this, smears stained with special stains such as gomori methenamine silver (GMS), periodic acid – Schiff (PAS), iron hematoxylin, giemsa and papanicolaou can be made.

However, some authors affirm that these stains do not allow the structures of the microorganism to be well visualized, making it difficult to observe the nucleus because the vacuoles overlap.

Therefore, highly skilled professionals are needed for the identification of amoeba, since it is easily confused with histiocytes. For this reason, they recommend making fresh preparations, making mouthwashes with 3 mL of saline solution.

Subsequently, the sample is centrifuged and a drop of sediment is dispensed onto a slide, covering it with a cover sheet.

In this simple preparation, all the structures of the parasite can be visualized in vivo, where the characteristic movement of the trophozoites can even be appreciated.

Transmission

It can be transmitted through intimate contact with the saliva of people with Entamoeba gingivalis in their mouth.

This means that Entamoeba gingivalis is transmitted by deep kissing, drinking or eating with glasses and cutlery contaminated with saliva from people that contain the protozoan in their oral cavity. TAlso for the shared use of toothbrushes.

Risk factor’s

Risk factors for presenting the parasite with active symptoms in the oral cavity include:

  • The condition of a diabetic patient
  • Smoking
  • Chemotherapy
  • Poor oral hygiene
  • Stomatological alterations
  • HIV positive patients.

All of them are believed to play an essential role in the proliferation of the microorganism.

Lifecycle

The Entamoeba gingivalis is played by longitudinal binary division and no sexual reproduction. The cycle begins when a susceptible person is exposed to saliva contaminated with the parasite, either direct or indirect.

Once the Entamoeba reaches the new host, the trophozoite begins its division. If it gets favorable conditions, it settles in various ecological niches, where it remains.

They can disappear if you maintain good oral hygiene.

Prevention

Oral hygiene and good dental control is recommended to maintain good oral health.

You should go to the dentist when certain manifestations occur such as: halitosis, very red gums, frequent bleeding and itching in the gingival area.

This will prevent these discomforts from progressing to severe periodontal diseases.

Treatment

Non-surgical periodontal treatment could reduce the number of Entamoeba gingivalis in the oral environment of patients with chronic periodontitis.

An in vitro study demonstrated that metronidazole kills E. gingivalis at a concentration ≥ 4 mg / L.

Likewise, an in vivo clinical study reported a 64% to 26% decrease in E. gingivalis in periodontal disease, after placing a treatment with oral metronidazole, 750 mg daily for 7 days.

References

  1. Bonner M, Amard V, Bar-Pinatel C, et al. Detection of the amoeba  Entamoeba gingivalis  in periodontal pockets. Parasite . 2014; 21:30.
  2. Fuentes R, Sánchez M, Contreras C, Hernández-Sierra F. Prevalence and epidemiological association of the oral protozoa Entamoeba gingivalis and Trichomonas tenax in Mexican children. ADM Magazine 2008; 65 (5): 259-262.
  3. García G, Ramos F, Hernández L, Yáñez J and Gaytán P. A New subtype of Entamoeba gingivalis : “ E. gingivalis ST2, Kamaktti variant”. Parasitol Res. 2018; 117 (4): 1277-1284.
  4. Wikipedia contributors. Entamoeba gingivalis. Wikipedia, The Free Encyclopedia. March 22, 2018, 19:08 UTC. Available at: wikipedia.org/. Accessed September 14, 2018.
  5. Rashidi F, Haerian A, Fattahi A, Haerian A, and Zafarbakhsh A. The Effect of Nonsurgical Periodontal Therapy on  Trichomonas Tenax  and  Entamoeba Gingivalis  in Patients with Chronic Periodontitis.  Journal of Dentistry . 2016; 17 (3), 171–176.
  6. Eloufir F, Khelaifia S, Aboudharam G, Drancourt M. In Vitro Activity of Metronidazole against Entamoeba gingivalis . J Infect Dis Ther . 2014; 2: 170.

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