Diagnosis of intestinal and extraintestinal amebiasis. Acta Med Colomb [online]. ISSN As well as to unify the diagnostic criteria of this parasitosis known as a public health problem, and as a consequence of that, optimize the quality of population care. Data source: there was a systematic search for the scientific literature Publisher in Spanish and English since until today, this selection started on the first semester of until , in the development of the line on intestinal and extra-intestinal amebiasis of the Medical School of the National University of Colombia.
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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. Other morphologically-identical Entamoeba spp. While the discussed species are morphologically-identical, E.
Non-pathogenic amebae e. Endolimax nana, I odamoeba buetschlii, other Entamoeba 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 with Entamoeba histolytica and E. Exposure to infectious cysts and trophozoites in fecal matter during sexual contact may also occur. Excystation occurs in the small intestine and trophozoites are released, which migrate to the large intestine.
Trophozoites may remain confined to the intestinal lumen A: noninvasive infection with individuals continuing to pass cysts in their stool asymptomatic carriers. Trophozoites can invade the intestinal mucosa B: intestinal disease , or blood vessels, reaching extraintestinal sites such as the liver, brain, and lungs C: extraintestinal disease. Trophozoites multiply by binary fission and produce cysts , and both stages are passed in the feces. Cysts can survive days to weeks in the external environment and remain infectious in the environment due to the protection conferred by their walls.
Trophozoites passed in the stool are rapidly destroyed once outside the body, and if ingested would not survive exposure to the gastric environment. Pathogenic Entamoeba species occur worldwide and are frequently recovered from fresh water contaminated with human feces.
The majority of amebiasis cases occur in developing countries. In industrialized countries, risk groups include men who have sex with men, travelers, recent immigrants, immunocompromised persons, and institutionalized populations.
Amebic colitis, or invasive intestinal amebiasis, occurs when the mucosa is invaded. Symptoms include severe dysentery and associated complications.
Severe chronic infections may lead to further complications such as peritonitis, perforations, and the formation of amebic granulomas ameboma. Amebic liver abscesses are the most common manifestation of extraintestinal amebiasis. Pleuropulmonary abscess, brain abscess, and necrotic lesions on the perianal skin and genitalia have also been observed. Pathogenic Entamoeba trophozoites have a single nucleus, which have a centrally placed karyosome and uniformly distributed peripheral chromatin.
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 classically associated with E. Note that erythrophagocytosis is rarely observed on stained smears.
Morphologic differentiation among these is possible, but potentially complicated, based on morphologic characteristics of the cysts and trophozoites. In culture, differential growth characteristics of E. Historically, differentiation of E. Molecular methods are currently recommended for distinguishing pathogenic Entamoeba species. Microscopic identification of cysts and trophozoites in the stool is the common method for diagnosing pathogenic Entamoeba species.
This can be accomplished using:. Trophozoites can also be identified in aspirates or biopsy samples obtained during colonoscopy or surgery. Antibody detection is most useful in patients with extraintestinal disease i. Antibody detection is of limited diagnostic value on patients from highly endemic areas that are likely to have prior exposure and seroconversion, but may be of more use on patients from areas where pathogenic Entamoeba spp.
Antigen detection during active infections 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. Detectable E.
Also, patients who have lived in highly endemic areas are likely to be seropositive due to past exposures. Although detection of IgM antibodies specific for E. No commercial antibody detection kits exist for E. Antigen detection may be useful as an adjunct to microscopic diagnosis in detecting parasites and to distinguish between pathogenic and nonpathogenic infections. However, utility is limited for frozen or fixed specimens and for post-treatment specimens.
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 conventional PCR-based assays is the method of choice for discriminating between E.
Some assays also can distinguish E. Comparison of real-time PCR rationales for differential laboratory diagnosis of amebiasis. J Clin Microbiol ; Cysts in unfixed stool samples are potentially infective. Ali, I. Intestinal amebae.
Clinics in Laboratory Medicine , 35 2 , pp. Heredia, R. Entamoeba moshkovskii perspectives of a new agent to be considered in the diagnosis of amebiasis. Acta Tropica , 3 , pp. Cutaneous Amebiasis: the importance of molecular diagnosis of an emerging parasitic disease. Leo, M. Evaluation of Entamoeba histolytica antigen and antibody point-of-care tests for the rapid diagnosis of amebiasis.
Journal of clinical microbiology , 44 12 , pp. DPDx is an educational resource designed for health professionals and laboratory scientists. For an overview including prevention, control, and treatment visit www.
Skip directly to site content Skip directly to page options Skip directly to A-Z link. Section Navigation. Minus Related Pages. Parasite Biology Image Gallery Laboratory Diagnosis Resources Causal Agents Several protozoan species in the genus Entamoeba colonize humans, but not all of them are associated with disease.
Life Cycle View Larger. Figure A: Cyst of E. Notice the chromatoid bodies with blunt, rounded ends arrow. Figure B: Cyst of E. Figure C: Cyst of E. Figure D: Cyst of E. Notice the chromatoid body with blunt, rounded ends arrow. Note the chromatoid body with blunt ends red arrow. Three nuclei are visible in the focal plane black arrows , and 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 arrows , and the cyst contains a chromatoid body with typically blunted ends red arrow.
Figure A: 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.
Figure B: Immature cyst of E. Image taken at x oil magnification and contributed by the Kansas Department of Health and Environment. Figure C: Immature cyst of E.
The cyst has large vacuoles and the chromatin around the nucleus is clumpy. Figure D: Immature cyst of E. These cysts range in size from Figure A: Trophozoite of E. Figure B: Trophozoite of E.
Figure C: Trophozoite of E. Figure D: Trophozoite of E. The vacuolated cytoplasm seen in this image may be the result of less than optimal preservation. Figure E: Trophozoite of E. Trophozoites of E.
Extra-intestinal Amebiasis: Clinical Presentation in a Non-Endemic Setting
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. Other morphologically-identical Entamoeba spp. While the discussed species are morphologically-identical, E. Non-pathogenic amebae e. Endolimax nana, I odamoeba buetschlii, other Entamoeba species are important because they may be confused with E.
Diagnostico de amebiasis intestinal y extraintestinal
Authors: Eric Houpt, M. Infection ranges from asymptomatic colonization of the large bowel to severe invasive intestinal and extra-intestinal disease. The parasite life cycle is relatively simple: humans orally ingest the cyst form from contaminated sources, excystation to the trophozoite form occurs in the small bowel, then the trophozoite either colonizes or invades the large bowel. When the trophozoite encysts the life cycle is complete and the organism can be transmitted