Entamoeba

A genus of ameba parasitic in the oral cavity, cecum, and large bowel of humans and other primates and in many domestic and wild mammals and birds; with the exception of E. histolytica, members of the genus appear to be relatively harmless inhabitants of the host. [G. entos, within + amoibe, change]

- E. buccalis former name for E. gingivalis.

- E. chattoni a species that does not produce symptoms; most commonly found in monkeys but occasionally has been identified in humans; cysts are uninucleate.

- E. coli nonpathogenic species of ameba that occurs in the large intestine of man, other primates, dogs, and possibly pigs; often confused with E. histolytica, but distinguished by nuclear details and by the number of nuclei and the form of chromatoidals in the cyst.

- E. dispar nonpathogenic species that occurs in the large intestine of humans; formerly considered E. histolytica, E. dispar is now considered a separate species; it is nonpathogenic and is not associated with symptomatic amebiasis in humans. Morphologically it resembles E. histolytica; however, the trophozoites are never found to contain ingested red blood cells.

- E. gingivalis a species of ameba found in the oral cavity of man, other primates, dogs, and cats; in humans, it is frequently associated with poor oral hygiene and its resultant diseases.

- E. hartmanni a species of ameba found in the large intestine of humans, other primates, and dogs; now considered to be a distinct species that is nonpathogenic and smaller than E. histolytica but otherwise indistinguishable from it; formerly called the “small race” of E. histolytica.

- E. histolytica a species of ameba that is the only distinct pathogen of the genus, the so-called “large race” of E. histolytica, causing tropical or amebic dysentery in humans and also in dogs (humans are the reservoir for canine infections). In humans, the organism may penetrate the epithelial tissues of the colon, causing ulceration (amebic dysentery); in a small proportion of these cases, the organism may reach the liver by the portal bloodstream and produce abscesses (hepatic amebiasis); in a fraction of these cases it may then spread to other organs, such as the lungs, brain, kidney, or skin and frequently be fatal. SEE ALSO: E. dispar.

- E. moshkovskii a species of ameba very similar to E. histolytica, probably not infective to man, but a cause of diagnostic difficulties since it has been recovered from human sewage and may be responsible for false-positive results in tests of sewage plant effluents.

- E. polecki a species of ameba commonly found in the intestines of pigs; also parasitizes monkeys, cattle, goats, sheep and dogs; also found in humans, where it does not produce symptoms; clinical importance lies in the possibility of confusing the organism with E. histolytica.

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Ent·amoe·ba .ent-ə-'mē-bə, 'ent-ə-. n a genus of ameboid protozoans (order Amoebida) that are parasitic in the vertebrate alimentary canal and esp. in the intestines and that include the causative agent (E. histolytica) of amebic dysentery see ENDAMOEBA

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n.

a genus of widely distributed amoebae, of which some species are parasites of the digestive tract of humans. E. histolytica invades and destroys the tissues of the intestinal wall, causing amoebic dysentery and ulceration of the gut wall (see also amoeboma); infection of the liver with this species (amoebic hepatitis) is common in tropical countries. E. coli is a harmless intestinal parasite; E. gingivalis, found within the spaces between the teeth, is associated with periodontal disease and gingivitis.

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Ent·amoe·ba (en″tə-meґbə) [ent- + ameba] a genus of ramicristate amebae of the order Amoebida, parasitic in many different animals; the organism has a vesicular nucleus with a small central karyosome and numerous peripheral chromatin granules attached to the nuclear membrane.