Although most cases of amebiasis are asymptomatic, dysentery and invasive extraintestinal disease can occur. Amebic liver abscess is the. Radiology. Jan;(1) Extraintestinal amebiasis. Juimo AG(1), Gervez F, Angwafo FF. Author information: (1)Department of Radiology, General . Scand J Infect Dis. ;25(6) Extra-intestinal amebiasis: clinical presentation in a non-endemic setting. Thorsen S(1), Rønne-Rasmussen J, Petersen E.
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Several protozoan species in the genus Entamoeba colonize humans, but not all of them are associated with disease. Entamoeba histolytica is well recognized as a pathogenic ameba, associated with intestinal and extraintestinal infections.
The other species are important because they may be confused with E. Cysts and trophozoites are passed in feces. Cysts are typically found in formed stool, whereas trophozoites are typically found in diarrheal stool. Infection by Entamoeba histolytica occurs by ingestion of mature cysts in fecally contaminated food, water, or hands.
Excystation occurs in the small intestine and trophozoites are released, which migrate to the large intestine.
The trophozoites multiply by binary fission and produce cystsand both stages are passed in the edtraintestinal. Because of the protection conferred by their 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 exposure to the gastric environment.
In many cases, the trophozoites remain confined to the intestinal lumen: In some patients the trophozoites invade the intestinal mucosa: It has been established that the invasive and noninvasive forms represent two separate species, respectively E. These two species are morphologically indistinguishable unless E. Transmission can also occur through exposure to fecal matter during sexual contact in which case not only cysts, but also trophozoites could prove infective.
Worldwide, with higher incidence of amebiasis in developing countries. In industrialized countries, risk groups include male homosexuals, travelers and recent immigrants, and ameniasis populations.
Notice the chromatoid bodies with blunt, rounded ends arrow. Notice the chromatoid body with blunt, rounded ends arrow.
Amebixsis the chromatoid body with blunt ends red arrow. Three nuclei are visible in the focal plane black arrowsand the cyst contains a chromatoid body with typically blunted ends red arrow.
The chromatoid body in this image is particularly well demonstrated. Two nuclei are visible in the focal plane black arrowsand the cyst contains a chromatoid body with typically blunted ends red arrow.
Immature cyst of E. The specimen was preserved in poly-vinyl alcohol PVA and stained with trichrome. PCR was performed on this specimen to differentiate between E. Image taken at x oil magnification and contributed by the Kansas Department of Health and Environment.
The cyst has large vacuoles and the chromatin around the nucleus is clumpy. These cysts range in size from This typical appearance of the nucleus is not always observed as some trophozoites can have nuclei with an eccentric karyosome and unevenly distributed peripheral chromatin. Erythrophagocytosis ingestion of red blood cells by the parasite is the only morphologic characteristic that can be used to differentiate E.
Extra-intestinal amebiasis: clinical presentation in a non-endemic setting.
However, erthrophagocytosis is not typically observed on stained smears of E. The vacuolated cytoplasm seen in this image may be the result of less than optimal preservation. The ingested erythrocytes appear as dark inclusions. The parasite above shows nuclei that have the typical small, centrally located karyosome, and thin, uniform peripheral chromatin.
The parasites above show nuclei that have the typical small, centrally located karyosome, and thin, uniform peripheral chromatin. Entamoeba histolytica must be differentiated from other intestinal protozoa including: Differentiation is possible, but not always easy, based on morphologic characteristics of the cysts and trophozoites.
The nonpathogenic Entamoeba disparhowever, is morphologically identical to E. Molecular methods are also useful in distinguishing between E. Microscopic identification of cysts and trophozoites in the stool is the common method for diagnosing E. This can be accomplished using:. Antibody detection is most useful in patients with extraintestinal disease i. Antigen detection may be useful as an adjunct to microscopic diagnosis in detecting parasites and can distinguish between pathogenic and nonpathogenic infections.
The indirect hemagglutination IHA test has been replaced by commercially available EIA test kits for routine serodiagnosis of amebiasis.
Antigen consists of a crude soluble extract of axenically cultured organisms. The EIA test detects antibody specific for E. If antibodies are not detectable in patients with an acute presentation of suspected amebic liver abscess, a second specimen should be drawn days later.
If the second specimen does not show seroconversion, other agents should be considered. However, the simplicity of the procedure makes it ideal for the laboratory that has only an occasional specimen to test. Although detection of IgM antibodies specific for E.
Antigen detection may be useful as an adjunct to microscopic diagnosis in detecting parasites and to distinguish between pathogenic and nonpathogenic infections.
Recent studies indicate improved sensitivity and specificity of fecal antigen assays with the use of monoclonal antibodies which can distinguish between E. At least one commercial kit is available which detects only pathogenic E. In reference diagnosis laboratories, molecular analysis by PCR-based assays is the method of choice for discriminating between the pathogenic species E.
Figure contributed by Assist. DPDx is an education resource designed for health professionals and laboratory scientists.
For an overview including prevention and control visit www. Skip directly to search Skip directly to A to Z list Skip directly to navigation Skip directly to page options Skip directly to site content. Enter Email Address What’s this? Recommend on Facebook Tweet Share Compartir. Life Cycle Cysts and trophozoites amebiaais passed in feces.
Geographic Distribution Worldwide, with higher incidence of amebiasis in developing countries. Antigen Detection Antigen detection may be useful as an adjunct to microscopic diagnosis in detecting parasites and to distinguish extraintesinal pathogenic and nonpathogenic infections.
Comparison of PCR, isoenzyme analysis, and antigen detection for diagnosis of Entamoeba histolytica infection. J Clin Microbiol ; Amebiasls Diagnosis Conventional PCR In reference diagnosis laboratories, molecular analysis by PCR-based assays is the method of choice for discriminating between the pathogenic species E.
Lanes 1 — 4: Diagnostic band size — bp. Lanes 6 — 9: Lanes 1 and 6: Lanes 2 and 7: Lanes 3 and 8: Specimen from a patient with a liver abscess positive with E. Lanes 4 and 9: Specimen from an asymptomatic patient positive with E. Molecular base pair standard, bp ladder from to 1, bp. Differentiation of pathogenic Entamoeba histolytica from other intestinal protozoa by riboprinting. Arch Med Res ; Comparison of real-time PCR ajebiasis for differential laboratory diagnosis of aamebiasis.
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