Entamoeba coli (along with Endolimax nana, Ent. hartmanni, Ent. polecki, and Iodamoeba buetschlii) are generally considered nonpathogenic and reside in the large intestine of a human host. Both cysts and trophozoites of these species are passed in stool and considered diagnostic. Cysts are typically found in formed stool, whereas trophozoites (the active stage) are typically found in diarrheal stool. Colonization of the nonpathogenic amebae occurs after ingestion of mature cysts in fecally-contaminated food, water, or fomites (i.e., inanimate objects or substances capable of transferring pathogens). Excystation (release of the trophozoite from the cyst) occurs in the small intestine and the trophozoites migrate to the large intestine. The trophozoites multiply by binary fission and both trophozites and cysts are passed in the feces. Because of the protection conferred by their cell walls, the cysts can survive days to weeks in the external environment and are responsible for transmission. Trophozoites passed in the stool are rapidly destroyed once outside the body and if ingested would not survive the gastric environment. Entamoeba coli has a worldwide distribution. (Centers for Disease Control Parasites and Health Website)
Entamoeba coli is a non-pathogenic species of Entamoeba that frequently exists as a commensal parasite in the human gastrointestinal tract. E. coli (not to be confused with the bacterium Escherichia coli) is important in medicine because it can be confused during microscopic examination of stained stool specimens with the pathogenic Entamoeba histolytica. While this differentiation is typically done by visual examination of the parasitic cysts via light microscopy, new methods using molecular biology techniques have been developed.
The presence of E.coli is not cause in and of itself to seek treatment as it is considered harmless. However, when a person becomes infected with this benign entamoeba, other pathogenic organisms may have been introduced as well, and these other pathogens might cause infection or illness.
E. Coli trophozoites can be distinguished by their wide and tapered pseudopodia. They are often mistaken for E. histolytica due to their overlap in size. The cysts are distinguished by noticing the eight nuclei found in the mature form.
- Sodeman WA (1996). "Intestinal Protozoa: Amebas". Baron's Medical Microbiology (Baron S et al., eds.) (4th ed.). Univ of Texas Medical Branch. ISBN 0-9631172-1-1.
- Verweij JJ, Laeijendecker D, Brienen EA, van Lieshout L, Polderman AM (2003). "Detection and identification of entamoeba species in stool samples by a reverse line hybridization assay". J. Clin. Microbiol. 41 (11): 5041–5. doi:10.1128/JCM.41.11.5041-5045.2003. PMC 262518. PMID 14605136.
- "Intestinal and Luminal Protozoa". Retrieved 2008-12-19.
- "Nonpathogenic Intestinal Amebae Infection". Parasitic Disease Information. CDC. 2004-09-29. Retrieved 2007-08-10.
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