Entamoeba histolytica - wikipedia Entamoeba histolytica Entamoeba histolytica Entamoeba histolytica trophozoite Scientific classification Domain : Eukaryota ( unranked ) : Amoebozoa Subphylum : Conosa Class : Archamoebae Family : Entamoebidae Genus : Entamoeba Species : E. histolytica Binomial name Entamoeba histolytica Schaudinn, 1903 Life - cycle of Entamoeba histolytica Entamoeba histolytica is an anaerobic parasitic amoebozoa, part of the genus Entamoeba. Predominantly infecting humans and other primates causing amoebiasis, E. histolytica is estimated to infect about 50 million people worldwide. Previously, it was thought that 10 % of the world population was infected, but these figures predate the recognition that at least 90 % of these infections were due to a second species, E. dispar. Mammals such as dogs and cats can become infected transiently, but are not thought to contribute significantly to transmission. The word histolysis literally means disintegration and dissolution of organic tissues. Contents 1 Transmission 2 High - risk individuals 3 Genome 4 Pathology 5 Pathogen interaction 6 Diagnosis 7 Treatment 8 Meiosis 9 See also 10 References 11 External links Transmission The active ( trophozoite ) stage exists only in the host and in fresh loose feces ; cysts survive outside the host in water, in soils, and on foods, especially under moist conditions on the latter. The infection can occur when a person puts anything into their mouth that has touched the feces of a person who is infected with E. histolytica, swallows something, such as water or food, that is contaminated with E. histolytica, or swallows E. histolytica cysts ( eggs ) picked up from contaminated surfaces or fingers. The cysts are readily killed by heat and by freezing temperatures, and survive for only a few months outside of the host. When cysts are swallowed they cause infections by excysting ( releasing the trophozoite stage ) in the digestive tract. The pathogenic nature of E. histolytica was first reported by Lösch in 1875, but it was not given its Latin name until Fritz Schaudinn described it in 1903. E. histolytica, as its name suggests ( histo -- lytic = tissue destroying ), is pathogenic ; infection can be asymptomatic or can lead to amoebic dysentery or amoebic liver abscess. Symptoms can include fulminating dysentery, bloody diarrhea, weight loss, fatigue, abdominal pain, and amoeboma. The amoeba can actually ' bore ' into the intestinal wall, causing lesions and intestinal symptoms, and it may reach the blood stream. From there, it can reach different vital organs of the human body, usually the liver, but sometimes the lungs, brain, spleen, etc. A common outcome of this invasion of tissues is a liver abscess, which can be fatal if untreated. Ingested red blood cells are sometimes seen in the amoeba cell cytoplasm. High - risk individuals It is more common in people who live in tropical areas with poor sanitary conditions, male homosexuals, travelers and recent immigrants, and institutionalized populations. Genome The E. histolytica genome was sequenced, assembled, and automatically annotated in 2005. The genome was reassembled and reannotated in 2010. The 20 million basepair genome assembly contains 8,160 predicted genes ; known and novel transposable elements have been mapped and characterized, functional assignments have been revised and updated, and additional information has been incorporated, including metabolic pathways, Gene Ontology assignments, curation of transporters, and generation of gene families. The major group of transposable elements in E. histolytica are non-LTR retrotransposons. These have been divided in three families called EhLINEs and EhSINEs ( EhLINE1, 2, 3 and EhSINE1, 2, 3 ). EhLINE1 encode an endonuclease ( EN ) protein ( in addition to reverse transcriptase and nucleotide - binding ORF1 ), which have similarity with bacterial restriction endonuclease. This similarity with bacterial protein indicates that transposable elements have been acquired from prokaryotes by horizontal gene transfer in this protozoan parasite. Pathology In the vast majority of cases, infection is asymptomatic and the carrier is unaware they are infected. However, in an estimated 10 % of cases E. histolytica causes disease. Once the trophozoites are excysted they colonize the large bowel, remaining on the surface of the mucus layer and feeding on bacteria and food particles. Occasionally, and in response to unknown stimuli, trophozoites move through the mucus layer where they come in contact with the epithelial cell layer and start the pathological process. E. histolytica has a lectin that binds to galactose and N - acetylgalactosamine sugars on the surface of the epithelial cells, The lectin normally is used to bind bacteria for ingestion. The parasite has several enzymes such as pore forming proteins, lipases, and cysteine proteases, which are normally used to digest bacteria in food vacuoles but which can cause lysis of the epithelial cells by inducing cellular necrosis and apoptosis when the trophozoite comes in contact with them and binds via the lectin. Enzymes released allow penetration into intestinal wall and blood vessels, sometimes on to liver and other organs. The trophozoites will then ingest these dead cells. This damage to the epithelial cell layer attracts human immune cells and these in turn can be lysed by the trophozoite, which releases the immune cell 's own lytic enzymes into the surrounding tissue, creating a type of chain reaction and leading to tissue destruction. This destruction manifests itself in the form of an ' ulcer ' in the tissue, typically described as flask - shaped because of its appearance in transverse section. This tissue destruction can also involve blood vessels leading to bloody diarrhea, amebic dysentery. Occasionally, trophozoites enter the bloodstream where they are transported typically to the liver via the portal system. In the liver a similar pathological sequence ensues, leading to amebic liver abscesses. The trophozoites can also end up in other organs, sometimes via the bloodstream, sometimes via liver abscess rupture or fistulas. In all locations, similar pathology can occur. Pathogen interaction E. histolytica may modulate the virulence of certain human viruses and is itself a host for its own viruses. For example, AIDS accentuates the damage and pathogenicity of E. histolytica. On the other hand, cells infected with HIV are often consumed by E. histolytica. Infective HIV remains viable within the amoeba, although fortunately there has been no proof of human reinfection from amoeba carrying this virus. A burst of research on viruses of E. histolytica stems from a series of papers published by Diamond et al. from 1972 to 1979. In 1972, they hypothesized two separate polyhedral and filamentous viral strains within E. histolytica that caused cell lysis. Perhaps the most novel observation was that two kinds of viral strains existed, and that within one type of amoeba ( strain HB - 301 ) the polyhedral strain had no detrimental effect but led to cell lysis in another ( strain HK - 9 ). Although Mattern et al. attempted to explore the possibility that these protozoal viruses could function like bacteriophages, they found no significant changes in Entamoeba histolytica virulence when infected by viruses. However, no newer published research has been conducted on this species since. Diagnosis Diagnosis is confirmed by microscopic examination for trophozoites or cysts in fresh or suitably preserved faecal specimens, smears of aspirates or scrapings obtained by proctoscopy, and aspirates of abscesses or other tissue specimen. A blood test is also available but is only recommended when your healthcare provider thinks that your infection may have spread beyond the intestine ( gut ) to some other organ of your body, such as the liver. However, this blood test may not be helpful in diagnosing your current illness because the test can be positive if you had amebiasis in the past, even if you are not infected now. Amoebic intestinal ulcer caused by E. histolytica Trophozoites of E. histolytica with ingested erythrocytes E. histolytica cyst Immature E. histolytica cyst ( mature cysts have 4 nuclei ) Multiplication by binary fission E. hystolytica drawing Treatment There are a number of effective medications. Generally several antibiotics are available to treat entamoeba histolytica. The infected individual will be treated with only one antibiotic if the E. histolytica infection has not made the person sick and most likely be prescribed with two antibiotics if the person has been feeling sick. Otherwise, below are other options for treatments. Intestinal infection : Usually nitroimidazole derivatives are used because they are highly effective against the trophozoite form of the amoeba. Since they have little effect on amoeba cysts, usually this treatment is followed by an agent ( such as paromomycin or diloxanide furoate ) that acts on the organism in the lumen. Liver abscess : In addition to targeting organisms in solid tissue, primarily with drugs like metronidazole and chloroquine, treatment of liver abscess must include agents that act in the lumen of the intestine ( as in the preceding paragraph ) to avoid re-invasion. Surgical drainage is usually not necessary except when rupture is imminent. People without symptoms : For people without symptoms ( otherwise known as carriers, with no symptoms ), non endemic areas should be treated by paromomycin, and other treatments include diloxanide furoate and iodoquinol. There have been problems with the use of iodoquinol and iodochlorhydroxyquin, so their use is not recommended. Diloxanide furoate can also be used by mildly symptomatic persons who are just passing cysts. Genus and species Entamoeba histolytica Etiologic agent of : Amoebiasis ; amoebic dysentery ; extraintestinal amoebiasis, usually amoebic liver abscess ; `` anchovy sauce '' ) ; amoeba cutis ; amoebic lung abscess ( `` liver - colored sputum '' ) Infective stage Tetranucleated cyst ( having 4 nuclei ) Definitive host Human Portal of entry Mouth Mode of transmission Ingestion of mature cyst through contaminated food or water Habitat Colon and cecum Pathogenic stage Trophozoite Locomotive apparatus Pseudopodia ( `` false foot '' `` ) Motility Active, progressive and directional Nucleus ' Ring and dot ' appearance : peripheral chromatin and central karyosome Mode of reproduction Binary fission Pathogenesis Lytic necrosis ( it looks like `` flask - shaped '' holes in Gastrointestinal tract sections ( GIT ) Type of encystment Protective and Reproductive Lab diagnosis Most common is direct fecal smear ( DFS ) and staining ( but does not allow identification to species level ) ; enzyme immunoassay ( EIA ) ; indirect hemagglutination ( IHA ) ; Antigen detection -- monoclonal antibody ; PCR for species identification. Sometimes only the use of a fixative ( formalin ) is effective in detecting cysts. Culture : From faecal samples - Robinson 's medium, Jones ' medium Treatment Metronidazole for the invasive trophozoites PLUS a lumenal amoebicide for those still in the intestine. Paromomycin ( Humatin ) is the luminal drug of choice, since Diloxanide furoate ( Furamide ) is not commercially available in the USA or Canada ( being available only from the Centers for Disease Control and Prevention ). A direct comparison of efficacy showed that Paromomycin had a higher cure rate. Paromomycin ( Humatin ) should be used with caution in patients with colitis, as it is both nephrotoxic and ototoxic. Absorption through the damaged wall of the intestinal tract can result in permanent hearing loss and kidney damage. Recommended dosage : Metronidazole 750 mg three times a day orally, for 5 to 10 days FOLLOWED BY Paromomycin 30 mg / kg / day orally in 3 equal doses for 5 to 10 days or Diloxanide furoate 500 mg 3 times a day orally for 10 days, to eradicate lumenal amoebae and prevent relapse. Trophozoite stage Pathognomonic / diagnostic feature Ingested RBC ; distinctive nucleus Cyst Stage Chromatoidal body ' Cigar ' shaped bodies ( made up of crystalline ribosomes ) Number of nuclei 1 in early stages, 4 when mature Pathognomonic / diagnostic feature ' Ring and dot ' nucleus and chromatoid bodies Meiosis In sexually reproducing eukaryotes, homologous recombination ( HR ) ordinarily occurs during meiosis. The meiosis - specific recombinase, Dmc1, is required for efficient meiotic HR, and Dmc1 is expressed in E. histolytica. The purified Dmc1 from E. histolytica forms presynaptic filaments and catalyzes ATP - dependent homologous DNA pairing and DNA strand exchange over at least several thousand base pairs. The DNA pairing and strand exchange reactions are enhanced by the eukaryotic meiosis - specific recombination accessory factor ( heterodimer ) Hop2 - Mnd1. These processes are central to meiotic recombination, suggesting that E. histolytica undergoes meiosis. Several other genes involved in both mitotic and meiotic HR are also present in E. histolytica. HR is enhanced under stressful growth conditions ( serum starvation ) concomitant with the up - regulation of HR - related genes. Also, UV irradiation induces DNA damage in E. histolytica trophozoites and activates the recombinational DNA repair pathway. In particular, expression of the Rad51 recombinase is increased about 15-fold by UV treatment. See also List of parasites ( human ) References ^ Jump up to : Ryan KJ, Ray CG, eds. ( 2004 ). Sherris Medical Microbiology ( 4th ed. ). McGraw Hill. pp. 733 -- 8. ISBN 0 - 8385 - 8529 - 9. Jump up ^ `` Amoebiasis '' ( PDF ). Wkly. Epidemiol. Rec. 72 ( 14 ) : 97 -- 9. April 1997. PMID 9100475. Jump up ^ `` Entamoeba histolytica ''. Centers for Disease & Prevention. Center for Disease & Prevention. Retrieved 24 October 2017. Jump up ^ American Water Works Association ( June 2006 ). Waterborne Pathogens. American Water Works Association. ISBN 978 - 1 - 58321 - 403 - 9. Jump up ^ Nespola, Benoît ; Betz, Valérie ; Brunet, Julie ; Gagnard, Jean - Charles ; Krummel, Yves ; Hansmann, Yves ; Hannedouche, Thierry ; Christmann, Daniel ; Pfaff, Alexander W. ; Filisetti, Denis ; Pesson, Bernard ; Abou - Bacar, Ahmed ; Candolfi, Ermanno ( 2015 ). `` First case of amebic liver abscess 22 years after the first occurrence ''. Parasite. 22 : 20. doi : 10.1051 / parasite / 2015020. ISSN 1776 - 1042. PMC 4472968. PMID 26088504. Jump up ^ `` Parasites - Amebiasis - Entamoeba histolytica Infection ''. Retrieved 7 April 2017. Jump up ^ Loftus, B ; Anderson, I ; Davies, R ; Alsmark, UC ; Samuelson, J ; et al. ( 2005 ). `` The genome of the protist parasite Entamoeba histolytica ''. Nature. 433 ( 7028 ) : 865 -- 868. doi : 10.1038 / nature03291. PMID 15729342. Jump up ^ Lorenzi, H.A., Puiu, D., Miller, J.R., Brinkac, L.M., Amedeo, P., Hall, N., & Caler, E.V. ( 2010 ). New assembly, reannotation and analysis of the Entamoeba histolytica genome reveal new genomic features and protein content information. PLoS neglected tropical diseases, 4 ( 6 ), e716. Jump up ^ Caler, E & Lorenzi, H ( 2010 ). `` Entamoeba histolytica : Genome Status and Web Resources ''. Anaerobic Parasitic Protozoa : Genomics and Molecular Biology. Caister Academic Press. ISBN 978 - 1 - 904455 - 61 - 5. Jump up ^ Bakre, Abhijeet A. ; Rawal, Kamal ; Ramaswamy, Ram ; Bhattacharya, Alok ; Bhattacharya, Sudha ( 2005 ). `` The LINEs and SINEs of Entamoeba histolytica : Comparative analysis and genomic distribution ''. Experimental Parasitology. 110 ( 3 ) : 207 -- 213. doi : 10.1016 / j. exppara. 2005.02. 009. Jump up ^ Yadav, VP ; Mandal, PK ; Rao, DN ; Bhattacharya, S ( December 2009 ). `` Characterization of the restriction enzyme - like endonuclease encoded by the Entamoeba histolytica non-long terminal repeat retrotransposon EhLINE1 ''. The FEBS Journal. 276 ( 23 ) : 7070 -- 82. doi : 10.1111 / j. 1742 - 4658.2009. 07419. x. PMID 19878305. Jump up ^ `` Pathogenic Properties of Some Common Pathogens '' ( PDF ). MtSac.edu. Professor Cindy Anderson. Retrieved 24 October 2017. Jump up ^ Hung CC, Deng HY, Hsiao WH, Hsieh SM, Hsiao CF, Chen MY, Chang SC, Su KE ( Feb 2005 ). `` Invasive amebiasis as an emerging parasitic disease in patients with human immunodeficiency virus type 1 infection in Taiwan ''. Arch Intern Med. 165 ( 4 ) : 409 -- 415. doi : 10.1001 / archinte. 165.4. 409. PMID 15738369. Jump up ^ Brown M, Reed S, Levy JA, Busch M, McKerrow JH ( Jan 1991 ). `` Detection of HIV - 1 in Entamoeba histolytica without evidence of transmission to human cells ''. AIDS. 5 ( 1 ) : 93 -- 6. doi : 10.1097 / 00002030 - 199101000 - 00014. PMID 2059366. Jump up ^ Diamond LS, Mattern CF, Bartgis IL ( Feb 1972 ). `` Viruses of Entamoeba histolytica. I. Identification of transmissible virus - like agents ''. J. Virol. 9 ( 2 ) : 326 -- 41. PMC 356300. PMID 4335522. Jump up ^ `` Entamoeba histolytica ''. CDC.gov. Retrieved 24 October 2017. Jump up ^ `` Entamoeba histolytica ''. Centers for Disease Control & Prevention. CDC.gov. Retrieved 24 October 2017. Jump up ^ Kucik, CJ ; Martin, GL ; Sortor, BV ( Mar 1, 2004 ). `` Common intestinal parasites ''. American Family Physician. 69 ( 5 ) : 1161 -- 8. PMID 15023017. Jump up ^ Blessmann J, Tannich E ( October 2002 ). `` Treatment of asymptomatic intestinal Entamoeba histolytica infection ''. N. Engl. J. Med. 347 ( 17 ) : 1384. doi : 10.1056 / NEJM200210243471722. PMID 12397207. Jump up ^ Stanley SL ( March 2003 ). `` Amoebiasis ''. Lancet. 361 ( 9362 ) : 1025 -- 34. doi : 10.1016 / S0140 - 6736 ( 03 ) 12830 - 9. PMID 12660071. Jump up ^ `` Diloxanide ( Systemic ) ''. Retrieved 17 November 2011. ^ Jump up to : Kelso AA, Say AF, Sharma D, Ledford LL, Turchick A, Saski CA, King AV, Attaway CC, Temesvari LA, Sehorn MG ( 2015 ). `` Entamoeba histolytica Dmc1 Catalyzes Homologous DNA Pairing and Strand Exchange That Is Stimulated by Calcium and Hop2 - Mnd1 ''. PLoS ONE. 10 ( 9 ) : e0139399. doi : 10.1371 / journal. pone. 0139399. PMC 4589404. PMID 26422142. ^ Jump up to : López - Casamichana M, Orozco E, Marchat LA, López - Camarillo C ( 2008 ). `` Transcriptional profile of the homologous recombination machinery and characterization of the EhRAD51 recombinase in response to DNA damage in Entamoeba histolytica ''. BMC Mol. Biol. 9 : 35. doi : 10.1186 / 1471 - 2199 - 9 - 35. PMC 2324109. PMID 18402694. Jump up ^ Singh N, Bhattacharya A, Bhattacharya S ( 2013 ). `` Homologous recombination occurs in Entamoeba and is enhanced during growth stress and stage conversion ''. PLoS ONE. 8 ( 9 ) : e74465. doi : 10.1371 / journal. pone. 0074465. PMC 3787063. PMID 24098652. External links Wikimedia Commons has media related to Entamoeba histolytica. Entamoeba histolytica image library Entamoeba histolytica - Centers for Disease Control and Prevention CDC DPDx Parasitology Diagnostic Web Site LSHTM Entamoeba Homepage Entamoeba Genome Resource - AmoebaDB Entamoeba histolytica article from the US Food and Drug Administration 's Bad Bug Book Amoebozoal diseases ( A06, 006 ) Lobosea ( free - living ) Centramoebida Acanthamoeba Acanthamoeba keratitis Cutaneous acanthamoebiasis Granulomatous amoebic encephalitis Acanthamoeba infection Balamuthia mandrillaris Balamuthia amoebic encephalitis Balamuthia infection Flabellinea Sappinia diploidea / Sappinia pedata Sappinia amoebic encephalitis Conosa / Archamoebae Entamoeba histolytica Amoebiasis Amoebic dysentery Amoebic liver abscess Cutaneous amoebiasis Amoebic brain abscess Amebiasis cutis Entamoeba gingivalis Retrieved from `` https://en.wikipedia.org/w/index.php?title=Entamoeba_histolytica&oldid=812529635 '' Categories : Conosa Parasitic amoebozoa Taxa named by Fritz Schaudinn Hidden categories : Articles with ' species ' microformats All articles with unsourced statements Articles with unsourced statements from July 2017 Talk Contents About Wikipedia Wikispecies Azərbaycanca Català Čeština Dansk Deutsch Emiliàn e rumagnòl Español Euskara فارسی Français Galego Հայերեն Bahasa Indonesia Italiano עברית ქართული Magyar Nederlands 日本 語 Norsk Polski Português Русский Simple English Slovenščina Српски / srpski Srpskohrvatski / српскохрватски Suomi Svenska Türkçe Tiếng Việt 中文 Edit links This page was last edited on 28 November 2017, at 10 : 11. 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Question: where does excystation of mature entamoeba histolytica cysts occur
Answer: digestive tract