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PubMed2004

Entamoeba struthionis n.sp. (Sarcomastigophora: Endamoebidae) from ostriches (Struthio camelus).

In the present work we identify the species of Entamoeba from ostriches (Struthio camelus). The complete sequence of the small subunit ribosomal RNA gene from this organism has been compared with those published for other species of the genus and clear differences have been found. These results confirm previous data which showed differences on parasite morphology and class of host with the other Entamoeba species. Taking all these data together, it can be concluded that the organism from ostriches is a new species whose proposed name is Entamoeba struthionis n.sp. This species probably infects rheas (Rhea americana), but genetic analysis of isolates from this host should be performed to confirm morphological data. Also, comparison of gene sequences with data from other authors on cysts recovered from human stool samples showed the possibility that this amoeba may affect humans. Further studies are needed to determine the risk of transmission of this new species to humans.

Animals↗
PubMed2004

Amebae and ciliated protozoa as causal agents of waterborne zoonotic disease.

The roles free-living amebae and the parasitic protozoa Entamoeba histolytica and Balantidium coli play as agents of waterborne zoonotic diseases are examined. The free-living soil and water amebae Naegleria fowleri, Acanthamoeba spp., and Balamuthia mandrillaris are recognized etiologic agents of mostly fatal amebic encephalitides in humans and other animals, with immunocompromised and immunocompetent hosts among the victims. Acanthamoeba spp. are also agents of amebic keratitis. Infection is through the respiratory tract, breaks in the skin, or by uptake of water into the nostrils, with spread to the central nervous system. E. histolytica and B. coli are parasitic protozoa that cause amebic dysentery and balantidiasis, respectively. Both intestinal infections are spread via a fecal-oral route, with cysts as the infective stage. Although the amebic encephalitides can be acquired by contact with water, they are not, strictly speaking, waterborne diseases and are not transmitted to humans from animals. Non-human primates and swine are reservoirs for E. histolytica and B. coli, and the diseases they cause are acquired from cysts, usually in sewage-contaminated water. Amebic dysentery and balantidiasis are examples of zoonotic waterborne infections, though human-to-human transmission can occur. The epidemiology of the diseases is examined, as are diagnostic procedures, anti-microbial interventions, and the influence of globalization, climate change, and technological advances on their spread.

Acanthamoeba↗
PubMed2002

Protozoon infections and intestinal permeability.

Intestinal permeability (IP) studies using some macromolecules have been assumed to demonstrate the intactness of intestinal mucosa. The aim of the present study is to determine the changes in IP among patients with protozoan infections. Thirty nine patients with protozoan infections and ten healthy controls were enrolled in the study. Protozoa were diagnosed by Native-lugol, Richie and Trichrome staining of faeces. IP was evaluated by diethyl triamine penta acetic acid labeled with 99m Technetium (99mTc labeled DTPA) assay. The IP was found to have increased in patients with protozoan infections compared with control patients (7.20+/-5.52 vs. 4.47+/-0.65%, P=0.0017). The IP values were 9.91+/-10.05% in Giardia intestinalis group, 6.81+/-2.25% in Blastocystis hominis group, 5.78+/-2.84% in Entamoeba coli group. In comparison with the control group, the IP was significantly higher in G. intestinalis and B. hominis patients (P=0.0025, P=0.00037, respectively), but not in E. coli patients. In conclusion, the IP increases in patients with G. intestinalis and B. hominis but not with E. coli infection. This finding supports the view that IP increases during the course of protozoan infections which cause damage to the intestinal wall while non-pathogenic protozoan infections have no effect on IP. The increase in IP in patients with B. hominis brings forth the idea that B. hominis can be a pathogenic protozoan.

Adult↗
PubMed2003

Cockroaches (Periplaneta americana and Blattella germanica) as potential mechanical disseminators of Entamoeba histolytica.

Since cockroaches feed on feces, they may disseminate infective agents with the fecal-oral route. A field survey and experiments were conducted to determine the role of cockroaches in the dissemination of Entamoeba histolytica. Periplaneta americana (n=299) and Blattella germanica (n=29) were collected from 11 primary schools in an urban area of South Taiwan. E. histolytica/E. dispar cysts were found on the cuticle and/or in the digestive tract of P. americana (25.4%) whereas cysts were only isolated from the digestive tract of B. germanica (10.3%). E. histolytica cysts were found on the cuticle and/or in the digestive tract of both species after exposure to 1000 or 100 cysts/g feces for 24 h. These findings indicate that cockroaches may harbor the E. histolytica cysts and play a role as potential mechanical disseminators.

Animals↗
PubMed2000

RAPD in the analysis of isolates of Entamoeba histolytica.

Genetic variability in Entamoeba histolytica was analyzed by random amplified polymorphic DNA (RAPD) using ten arbitrary primers. Due to intrinsic characteristics of the RAPD technique only axenic samples were analyzed. since the presence of any microorganism in the cultures interfered in the DNA profile by generating RAPDs not pertaining to E. histolytica. The RAPD profiles of E. histolytica samples isolated from patients with different clinical manifestations from different regions of the Americas shared about 70% of the bands produced. These profiles were compared to those obtained for E. moshkorskii, and E. invadens. The combined data for the ten primers were used in the phenetic analysis of all the isolates studied by using the Dice similarity coefficient as the genetic distance measure between the samples. Three distinct groups could be separated by phenon line: one including E. moshkovskii samples, which shared > 90% of the RAPDs produced by the different primers; one consisting solely of E. invadens; and a third comprising samples of E. histolytica, which showed considerable intraspecific variability.

Animals↗
PubMed2002

Entamoeba histolytica: immunohistochemical study of hepatic amoebiasis in mouse. Neutrophils and nitric oxide as possible factors of resistance.

Studies in mice have not rendered conclusive data on cell and humoral factors to support the resistance of this rodent to Entamoeba histolytica infection. In Balb/c and C3H/HeJ mice inoculated with live or fixed trophozoites, we studied the evolution of the hepatic lesion, the kinetics of inflammatory cells, and the participation of some humoral factors in the development of the hepatic amoebic lesion. From the first hour, amoebae were surrounded by neutrophils containing inducible nitric oxide synthase (iNOS); macrophages also expressing iNOS appeared lately, whereas NK cells were not part of the inflammatory infiltrates. On the fourth day, neutrophils, macrophages, T and B lymphocytes, plasma cells, and some NK cells limited the lesions and anti-amoeba antibodies appeared when most parasites had been eliminated. Therefore, the resistance of the mice to E. histolytica probably lies in non-specific immune responses, among which the activation of neutrophils and the production of nitric oxide (NO) may be important amoebicide factors.

Animals↗
PubMedDate not supplied

Entamoeba histolytica: sequence conservation of the Gal/GalNAc lectin from clinical isolates.

The Gal/GalNAc lectin gene of Entamoeba histolytica is a major amebic virulence protein responsible for interaction with host tissues. We investigated sequence differences in the Gal/GalNAc lectin heavy subunit in three isolates from Bangladesh and one isolate from Georgia, each of which was determined to be genetically distinct by SREHP AluI digestion. Interestingly, we observed only slight genetic diversity in the lectin gene as compared with the HM1:IMSS laboratory strain, originally a clinical isolate from Mexico. Genetic conservation of the Gal/GalNAc lectin between isolates may reflect that the lectin is under strong functional selection or possibly, that E. histolytica is a clonal population. Sequence conservation of the lectin indicates that immune responses against it should be cross-protective.

Amino Acid Sequence↗
PubMed2002

Entamoeba histolytica: rapid identification and differentiation of Indian isolates by riboprinting.

Entamoeba histolytica infection still remains one of the major public health problem for developing countries like India. A rapid and accurate detection of this parasite is essential for prevention and control of amoebiasis. In this study, using the method of 'riboprinting' (PCR-RFLP of rRNA genes from amoeba) we have analysed 15 stool samples from symptomatic patients of amoebiasis. All 15 patients of clinical amoebiasis had E. histolytica in their stool and two of the samples also showed mixed infection of E. dispar. Apart from the known restriction enzyme sites within the amoeba SSU-rRNA genes, a new Sau3A site having a discriminatory value is identified in these E. histolytica isolates from India. Hence, it is possible to rapidly identify E. histolytica DNA and differentiating it from E. dispar using minute amounts of clinical stool samples, thus eliminating the laborious parasite culturing process. Thus, riboprinting is advantageous for clearcut identification of E. histolytica in order to decide an effective antiamoebic therapy.

Animals↗
PubMed2003

A virulence attenuated amoebapore-less mutant of Entamoeba histolytica and its interaction with host cells.

Entamoeba histolytica, the protozoan parasite which causes amoebiasis, is an exclusively human pathogen so developing a vaccine could effectively impact the spread of the disease. Recently we developed a genetically modified avirulent strain, termed G3, from the virulent E. histolytica strain HM-1:IMSS. The new strain lacks the important virulence factor, the amoebapore-A. The objective of our current study was to investigate the avirulence of the attenuated strain as well as to examine the antigenic and immunogenic responses of these trophozoites as potential candidates for a live vaccine. Functional assays were conducted to characterise the virulent behaviour of the G3 strain. This behaviour was compared to the virulent strain HM-1:IMSS and the non-virulent strain Rahman. Western blots were conducted to confirm the lack of amoebapore-A in the E. histolytica G3 strain and to demonstrate that it had no influence on the presence of other virulence factors. Results of these two sets of tests proved the G3 strain to be phenotypically similar to the avirulent Rahman strain while antigenically identical to the virulent HM-1:IMSS, apart from the lack of the amoebapore-A protein. Intraperitoneal immunisation of hamsters with G3 trophozoites compared to sham immunised hamsters resulted in IgG anti-HM-1:IMSS antibodies. The level of humoral response was variable and further testing has to take place before introducing this new strain as a vaccine.

Animals↗
PubMed1998

Entamoeba histolytica and Entamoeba dispar are distinct species; clinical, epidemiological and serological evidence.

The name of the causative organism of invasive amoebiasis, Entamoeba histolytica, was first introduced in 1903, even though this intestinal amoeba had been recognised since 1875. The marked disparity between the number of infected individuals and those with invasive amoebiasis resulted in a number of explanatory hypotheses being proposed. Although none of these were universally accepted, Brumpt's concept of two morphologically identical species gained increasing acceptance 50-60 years later when technology became available to investigate this anomaly. Sargeaunt spear-headed this drive by establishing the value of isoenzyme electrophoresis for studying the host-parasite relationship. From this foundation, incorporation of clinical, epidemiological and serological parameters to studies of the parasite resulted in the conclusion that a species complex comprising two morphologically identical amoebae was implicated with the disease. The two organisms have been named E. histolytica and Entamoeba dispar. The former is a pathogen and is responsible for invasive amoebiasis, while the latter is a gut commensal. Demonstration of the existence of this species complex has subsequently been confirmed by studies on the nucleic acids from several independent laboratories. The acceptance of E. histolytica and E. dispar as distinct species has had a major impact on our understanding of amoebiasis and its clinical management.

Animals↗
PubMed1995

Intestinal inflammation associated with flagellates in snakes.

The intestines of 51 snakes with histologically diagnosed or suspected amoebiasis were reinvestigated immunohistochemically with an Entamoeba invadens antibody. In 22 cases, trophozoites of Entamoeba invadens stained positively in the inflamed intestinal wall, but the protozoa visible in the pathologically changed intestines of a further 20 snakes were negative. On the basis of light and electron microscopical findings, these protozoa were identified as flagellates.

Animals↗
PubMed2002

Development of a diagnostic test for Entamoeba histolytica using idiotype expression in human.

The protozoan parasite Entamoeba histolytica is the etiological agent of human amebiasis. The pathology of the disease starts with the cytolysis of the host target cells by amoebae. It is initiated by the adhesion of trophozoites to the host cells, through surface lectin via specific receptors. These adherence lectins have been demonstrated to be highly conserved, and can be recognised by serum antibodies from patients with invasive amebiasis. Some of these molecules have been used as antigens in serologic studies, which has been very helpful in the diagnosis of invasive intestinal amebiasis. However, false-positive serologic reactivity can occur using E. histolytica extracts and purified antigens. Additional problems are because the extracts display a great enzymatic activity. Several diagnostic methods, using different molecules and techniques, have been described. However, the problem still remains since these tests are not capable of differentiating between amoebic liver abscess (ALA) and intestinal amebiasis.Here, the research has been addressed to the 66-kDa antigen, which is a part of the outer membrane proteins from the E. histolytica strain HM1-IMSS trophozoites. First of all, we characterized the 66-kDa antigen in order to prove the relevance. We found that the 66-kDa antigen is a part of the plasma membranes and is distributed rather homogeneously on the cell surface of trophozoites. Apparently, the 66-kDa antigen is a glycoprotein. Using a monoclonal antibody (MAb), we found 25% of inhibition in the erythrophagocytosis by the trophozoites. Starting form one monoclonal antibody, we prepared an anti-idiotype (anti-Id) antibody reagent, with the purpose of searching for the different expressions of the idiotype between the sera from ALA and the intestinal amebiasis patients. Moreover, we produced the antibody Ab3 that is capable of recognising the 66-kDa antigen; it means that the Ab2 displays the internal image of the antigen. We found that 91.6% of the serum from ALA patients displayed the expression of the Id. In contrast, 15.7% of the E. histolytica asymtomatic cyst carriers displayed the Id expression, 6.6% of the patients with another parasite infection, and 11% of the negative controls (serum from umbilical cords of newborn babies). Our results showed that the expression of the Id could be differentiated among the AHA patients from the other groups with a 91.6% sensibility and 88.3% specificity.

Animals↗
PubMed1987

Surgical aspects of parasitic disease in childhood.

This is a review article concerning the surgical aspects of parasitic disease in childhood. The surgeon encounters parasitic disease for a variety of reasons. Many forms of infestation produce or mimic anatomic diseases of the gastrointestinal tract. Others are characterized by soft tissue or visceral mass lesions, lymphadenopathy, portal hypertension, etc. The surgical aspects of parasitism extend to all subspecialties, including ophthalmology, gynecology, and plastic surgery.

Ascariasis↗
PubMed1985

Entamoeba polecki infection in Southeast Asian refugees: multiple cases of a rarely reported parasite.

Recently, Entamoeba polecki was identified for the first time in our parasitology laboratory in stool specimens from eight Southeast Asian refugees. This ameba has been reported infrequently in the Western world; most reported cases have been from the New Guinea region. In most previously described patients and in our patients, no definite gastrointestinal symptoms could be directly attributed to E. polecki infection. Morphologically, E. polecki may mimic the pathogen E. histolytica and also nonpathogens such as E. coli. These species are most readily distinguished by studying encysted forms. In contrast to E. histolytica and E. coli, E. polecki characteristically has uninucleate cysts. Both pigs and monkeys naturally harbor E. polecki, but four of the patients in this series had no apparent contact with these animals. Other modes of infection may be human-to-human transmission or acquisition from other domestic animals. Six of our eight patients were treated successfully with one course of metronidazole in a regimen similar to that used for E. histolytica infection. In the two other patients, repeated courses of therapy eradicated the infection. Because of the recent increase in number of Southeast Asian immigrants to the United States, E. polecki may be identified more frequently than in the past. Physicians and laboratory personnel should be familiar with this organism, because it may be confused with E. histolytica or may act as a pathogen.

Adolescent↗