Diagnosis of Amebiasis in Bangladesh
International Centre for Diarrheal Disease Research (ICDDR,B), Dhaka, Bangladesh. Archives of Medical Research
(Impact Factor: 2.65).
03/2006; 37(2):273-6. DOI: 10.1016/j.arcmed.2005.09.001
Diagnosis of amebiasis by microscopic identification of the parasite in stool and liver abscess pus is insensitive and unable to distinguish the invasive parasite E. histolytica from the commensal parasites such as E. dispar and E. moshkovskii. New approaches to the detection of E. histolytica are based on detection of E. histolytica-specific antigen and DNA in stool and other clinical samples. Several molecular diagnostic tests for diagnosis of amebiasis have been developed and used to diagnose E. histolytica in Bangladesh. We have compared the TechLab E. histolytica-specific antigen detection test with PCR assays and with isoenzyme analysis of cultured amebas. The PCR assays are based on amplification of the multi-copy small subunit ribosomal RNA gene of E. histolytica and E. dispar. PCR assays and antigen detection test had comparable sensitivities when performed directly on fresh stool specimens. The correlation of antigen detection with PCR assays for identification of E. histolytica was excellent. TechLab's E. histolytica- specific antigen detection test was both rapid and simple to perform, making it appropriate for use in the developing world, where amebiasis is most prevalent.
Available from: Attapon Cheepsattayakorn
- "The effect of microbiota on immune response to Entamoeba histolytica and its virulence is not yet known . The presence of cysts or trophozoites of amoeba in the stool does not imply that the disease is caused by Entamoeba histolytica as other two non-pathogenic species found in humans (Entamoeba dispar and Entamoeba moshkovskii) are morphologically indistinguishable but can be rapidly, accurately, and effectively diagnosed by a single-round PCR [1, 31, 32]. Other diagnostic methods include culture of Entamoeba histolytica, enzyme-linked immunosorbent assay (ELISA), indirect fluorescent antibody test (IFAT), and indirect hemagglutination test (IHA) [1, 31, 32]. "
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ABSTRACT: Parasitic infestations demonstrated a decline in the past decade as a result of better hygiene practices and improved socioeconomic conditions. Nevertheless, global immigration, increased numbers of immunocompromised people, international traveling, global warming, and rapid urbanization of the cities have increased the susceptibility of the world population to parasitic diseases. A number of new human parasites, such as Plasmodium knowlesi, in addition to many potential parasites, have urged the interest of scientific community. A broad spectrum of protozoal parasites frequently affects the respiratory system, particularly the lungs. The diagnosis of parasitic diseases of airway is challenging due to their wide varieties of clinical and roentgenographic presentations. So detailed interrogations of travel history to endemic areas are critical for clinicians and pulmonologists to manage this entity. The migrating adult worms can cause mechanical airway obstruction, while the larvae can cause airway inflammation. This paper provides a comprehensive treview of both protozoal and helminthic infestations that affect the airway system, particularly the lungs, including clinical and roentgenographic presentations, diagnostic tests, and therapeutic approaches.
Available from: Sumeeta Khurana
- "Amoebiasis is one of the most common causes of death from protozoan parasitic diseases, second to malaria (Calderaro et al., 2006). Worldwide 50 million people suffer from amoebiasis, developing disabling colitis or extraintestinal complications leading to 50,000– 100,000 deaths every year (Haque and Petri, 2006; WHO, 2007). "
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ABSTRACT: Entamoeba histolytica infection is associated with considerable morbidity and mortality in the form of intestinal and extraintestinal amoebiasis. No vaccine is yet available for amoebiasis. Heparan Sulphate Binding Proteins (HSBPs) from E. histolytica were evaluated for immunogenicity and protective efficacy in a Guinea pig model. Animals were immunized subcutaneously with 30 g of HSBP by three weekly inoculations. The immunogenicity of HSBP was determined by antibody response (IgG, IgM and IgA), splenocyte proliferation assay and in vitro direct amoebicidal assay with splenic lymphocytes and monocytes from vaccinated and control animals. The efficacy of the vaccine was evaluated by challenge infection to vaccinated and control animals by intra-caecal inoculation of E. histolytica trophozoites and comparing gross and histopathological findings in caeca of these animals. HSBP was found to induce specific anti-amoebic response as seen by specific antibody production and direct amoebicidal activity of splenocytes. The vaccine also showed partial protection against challenge infection in vaccinated animals as shown by mild / absent lesions and histopathological findings.
Available from: Helena Lúcia Carneiro Santos
- "A wide variety of PCR methods targeting different genes, including 18S rRNA gene, genes that codify for the 30-kDa antigen, serine-rich protein, chitinase, hemolysin, and the extra-chromosomal circular DNA, have been described for the detection and differentiation of E histolytica, E dispar [14-21] and more recently E. moshkovskii in human stools [22-24]. However, some of these studies reported false negative results when these techniques were compared to microscopy examination, most of the time when other Entamoeba species; e.g., E. hartmanii, E. poleckii, E. coli, were present [7,25-28]. DNA based approaches can be multiplexed to allow identification of multiple organisms simultaneously. "
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Six species of the genus Entamoeba, i.e., E. histolytica, E. dispar, E. moshkovskii, E. polecki, E. coli, and E. hartmanii can be found in human stools. Among these, only E. histolytica is considered to be pathogenic, causing intestinal and extra-intestinal disease, but it is morphologically identical to E. dispar and E. moshkovskii. In general, E. polecki, E. coli, and E. hartmanii can be differentiated morphologically from E. histolytica, but some of their diagnostic morphologic features may overlap creating issues for the differential diagnosis. Moreover, the previous inability to differentiate among Entamoeba species has limited epidemiologic information on E histolytica. The objective of this study was to develop a rapid, high-throughput screening method using Luminex technique for the simultaneous detection and differentiation of Entamoeba species.
PCR amplification was performed with biotinylated Entamoeba sp 18S rRNA gene primers, designed to amplify a fragment ranging from 382 to 429 bp of the Entamoeba spp studied. Regions of this fragment that could differentiate among E. histolytica, E. moshkovskii, E. dispar, E. hartmanii and E. coli were selected to design hybridization probes to link to Luminex beads. The assay was standardized with cloned DNA samples of each species and evaluated with 24 DNA extracts from samples obtained from individuals diagnosed with these amebas in their stools.
Using this approach we were able to correctly identify E. histoltyica, E. dispar, E hartmanni, E. coli and E. moshkovskii in all specimens studied. From twenty four samples tested by microscopy, PCR/DNA Sequencing and real-time PCR, 100% agreed with PCR-Luminex assay for identification of E. dispar, E. moshkovskii, E. hartmanni, E. histolytica, and E. coli.
These results show that this method could be used in the diagnostic detection of Entamoeba spp in fecal samples. This diagnostic test was useful to clearly distinguish E histolytica from other species and also to strengthen epidemiologic data on Entamoeba spp.
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