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PubMed1993

Biochemical and immunological studies on soluble antigens of Entamoeba histolytica.

The soluble antigens of Entamoeba histolytica trophozoites were analysed in detail by biochemical and immunochemical methods. The antigen was highly complex and heterogeneous as revealed by Sephacryl S-300 column chromatography, which showed four distinct fractions. The molecular mass of fractions FI, FII, FIII and FIV was 660, 170, 65 and 13 kDa, respectively. Protein was the major constituent in crude soluble antigen (CSA) and fractions FI and FII (67%, 80% and 90%, respectively). Polysaccharide was predominant in the FIII fraction (59%). Antigenic activity observed after different physico-chemical treatments revealed that CSA and FI antigens were predominantly glycoprotein in nature. However, the antigenicity of FIII antigen was greatly reduced after sodium meta-periodate treatment, whereas no alteration in reactivity was discerned after trypsin treatment. Sodium dodecyl sulphate-polyacryl-amide gel electrophoresis (SDS-PAGE) analysis demonstrated nearly 28 Coomassie blue bands for CSA and 20, 16, 15 and 3 polypeptide bands for the FI, FII, FIII and FIV fractions, respectively. The molecular mass of the polypeptides of these bands ranged from 210 to 20 kDa. Antigenic activity was observed in CSA and in the first three fractions, both in counter immunoelectrophoresis (CIEP) and in enzyme-linked immunosorbent assay (ELISA). However, the highest antigenic activity was noted in fraction FI. Major immunoreactive polypeptides of CSA and FI antigens against whole trophozoite antibody were observed in the 10- to 170-kDa regions. However, major differences in the immunoreactivity of the two antigens were noted at 116 and 14 kDa for FI antigen and at 84, 30 and 20 kDa for CSA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Phagocytosis and proteinase activity are not related to pathogenicity of E. histolytica.

To examine the relationship between phagocytosis, proteinase activity and pathogenicity of axenically grown trophozoites of E. histolytica strain HM-1:IMSS four different cultures were used: (1) a culture preserved in our laboratory for over 4 years, which lost its pathogenicity 3 years ago; (2) a culture passaged several times through hamster liver, which lost its pathogenicity recently; (3) a highly virulent culture supplied by another laboratory; and (4) amebas recovered from hamster liver abscesses caused by culture 3. Phagocytosis was measured as erythrophagocytosis. Proteinase activity was determined on azocasein. Pathogenicity was defined as the capacity to cause liver abscesses in hamsters. A negative correlation was found between phagocytic activity and pathogenicity, since amebas unable to cause liver abscesses had the highest phagocytic activity, whereas those recovered from liver abscesses had the lowest phagocytic activity. The percent of phagocytic amebas showed wide variations through a 2-month observation period, with no change in amebic pathogenicity. No correlation was found between the level of proteinase activity and pathogenicity. It is concluded that neither phagocytosis nor proteinase activity is an adequate marker of amebic pathogenicity.

Animals↗
PubMed1990

Increase of DNA content in tissue stages of Entamoeba histolytica strain SFL 3.

The DNA content of culture forms and tissue stages of pathogenic E. histolytica strain SFL 3 were measured photometrically after the nuclei had been stained with the fluorochrome BAO. As a control, the DNA guartity of E. histolytica strain HK 9 and E. invadens were determined by the same method and compared with reference values. Tissue stages were obtained from hamsters experimentally infected by intrahepatic injection of SFL 3 amoebae. Further studies concerning possible changes in the DNA content of tissue stages involved the following methods: (a) isolation of tissue stages from the liver, followed by distinct suspension periods. (b) Infected liver pieces were directly transferred into culture medium; amoebae emigrating therefrom were cultivated. The study demonstrated that tissue stages contained up to 4 times more DNA than did culture forms. After 3 h cultivation, the DNA content of tissue stages decreased to the level of culture forms. Possible reasons for this change are discussed.

Amebiasis↗
PubMed1990

Appendiceal infection by Entamoeba histolytica and Strongyloides stercoralis presenting like acute appendicitis.

A 58-year-old male from Puerto Rico who was taking orally administered cortisone analogs for chronic obstructive pulmonary disease presented with fever, absolute eosinophilia, right lower quadrant pain, and rebound tenderness associated with Strongyloides stercoralis infection of the appendix. A 37-year-old alcoholic male developed fever, right lower quadrant abdominal pain, and rebound tenderness because of infection of the appendix with Entamoeba histolytica. These are the seventh reported case of isolated amebic appendicitis and the ninth reported case of appendiceal involvement with Strongyloides. In all these cases the diagnosis was made only after surgery. Patients with unexplained right lower quadrant pain, particularly if immunosuppressed or with an appropriate travel history, should have stool examinations for ova and parasites. Early diagnosis and treatment may prevent life-threatening complications such as perforation and peritonitis.

Adult↗
PubMed1975

Pathogenicity of entamoeba histolytica.

The pathogenicity of Entamoeba histolytica is discussed from an immunologic point of view. The evidence that there is some "trigger" mechanism which converts a commensal dwelling organism into a tissue invasive pathogen is rejected as inadequate. The number of liver abscess cases in comparison with the number of intestinal amebic infections in a population is so low that this in itself suggests that tissue invasion is a rare event in the life history of the ameba. A review is made of the experimental evidence that some type of sensitization is necessary before ameba can invade tissue. In postulating an immunologic basis for the pathogenicity of ameba, a parallel between the behavior of malignant cells in the body and an amebic infection in the gut is made. An appealing hypothesis which deserves further research effort is that an altered immune response is the basis for the pathogenic mechanism in the host.

Antibody Formation↗
PubMedDate not supplied

Characterization of 20 Entamoeba histolytica strains isolated from patients with HIV infection.

Twenty Entamoeba histolytica strains from patients with HIV-1 infection were isolated and compared with E. histolytica strains from patients without HIV infection. The isoenzyme pattern of the hexokinase as well as the hybridization with known DNA-probes were used as markers for pathogenicity. According to these markers, all 20 strains could be regarded as being nonpathogenic. Direct measurements of the virulence were carried out: destruction of monolayer tissue culture cells, capacity of phagocytosis and the ability to induce liver abscesses in the hamster. The virulence of strains from HIV patients was comparable to that of E. histolytica strains which had been isolated from HIV-negative asymptomatic carriers. In agreement with this, none of the HIV-positive patients showed symptoms of an invasive amebiasis. By PRC, no HIV-1 proviral DNA could be evidenced in the E. histolytica strains which had been isolated from HIV patients.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Six enteropathogens isolated from a case of acute gastroenteritis.

Isolation of six different gastrointestinal pathogens (Entamoeba histolytica, Plesiomonas shigelloides, Campylobacter jejuni and three different Salmonella species [Salmonella typhimurium, Salmonella blockley and Salmonella hadar]) in the feces of a German female tourist suffering from acute diarrhoea after a trip to Bali.

Acute Disease↗
PubMed1996

Evaluation of an antigen-capture enzyme immunoassay for detection of Entamoeba histolytica in stool samples.

In order to identify the prevalence of Entamoeba histolytica in tourists with diarrhoea returning from countries of the developing world, sensitivity and specificity of a commercially available enzyme immunoassay (EIA) kit for the detection of Entamoeba histolytica coproantigen in stool were evaluated. Five hundred seventy-seven specimens from 469 patients were examined by microscopy and EIA. Sixty-two specimens from 49 patients were considered positive for Entamoeba histolytica. Compared with microscopic examination of stool samples, the EIA was found to be slightly more sensitive (90.3% vs. 87.1%) and was 97.7% specific for Entamoeba histolytica.

Animals↗
PubMed1998

Host-pathogen interaction in amebiasis and progress in vaccine development.

Entamoeba histolytica, the causative organism of invasive intestinal and extraintestinal amebiasis, infects approximately 50 million people each year, causing an estimated 40 to 100 thousand deaths annually. Because amebae only infect humans and some higher non-human primates, an anti-amebic vaccine could theoretically eradicate the organism. Uncontrolled epidemiologic studies indicate that acquired immunity to amebic infection probably occurs and that such a vaccine might be feasible. Application of molecular biologic techniques has led to rapid progress towards understanding how Entamoeba histolytica causes disease, and to the identification of several amebic proteins associated with virulence. These proteins are now being evaluated as potential vaccine components. Parenteral and oral vaccine preparations containing recombinant amebic proteins have been effective in preventing disease in a gerbil model of amebic liver abscess. Although systemic and mucosal cellular and humoral immunity both appear to play a role in protection against Entamoeba histolytica, the relative importance of each in the human immune response remains unknown. No animal model of intestinal amebiasis currently exists, moreover, so it has been impossible to evaluate protection against colonization and colitis. Further investigation of the fundamental mechanisms by which Entamoeba histolytica causes disease and of the human immune response to amebic infection is necessary to assess the true feasibility of an anti-amebic vaccine.

Animals↗
PubMedDate not supplied

Outbreak of Entamoeba histolytica and Giardia lamblia infections in travellers returning from the tropics.

Of 160 travellers from various regions in Italy who had taken part in a five-day organized trip to Phuket, Thailand, and been accommodated in the same luxury hotel, 17 showed either amebic abscess or colitis. A pretested questionnaire that focused on the consumption of foods and beverages well known to be a source of intestinal infection in endemic areas was available from these 17 patients as well as from 41 out of 74 asymptomatic travellers. Stool samples for parasitological examination were also available. In patients affected with amebic abscess, antibodies to Entamoeba histolytica were also determined. Overall, parasitological examinations were negative in eight (13.8%) patients, and 50 out of 58 (86.2%) were found to be positive. The prevalence of Giardia lamblia and E. histolytica infections was 67.2% and 72.4%, respectively, and 28 subjects (48.3%) were stool-positive for both of these protozoa. No other intestinal parasites were found. No particular food or beverage was consumed by all of the parasitized subjects and by none of the stool-negative individuals. However, the consumption of drinks with ice, ice cream and raw fruit in ice was significantly associated with E. histolytica and/or G. lamblia infections (Fisher's exact test, p ranging from 0.03 to 0.003).

Adult↗
PubMed1984

Protozoal enteric infections in homosexual men.

The prevalence of enteric protozoal infections was examined in a group of 200 homosexual men. Entamoeba histolytica (E. histolyt .) was found in 22.8%, apathogen amoeba in 54.5% and Giardia lamblia (G. lamblia) in 9.1% of the participants. Antibodies against E. histolyt . were significantly higher in subjects carrying E. histolyt . than in the group with apathogen amoeba and in uninfected participants. Clinical symptoms were not associated with protozoal infection. The analysis of a number of variables showed that oral-anal sex and promiscuity were the two most important risk factors for protozoal infection. The clinical significance of protozoal enteric infections and their possible relation to the acquired immune deficiency syndrome (AIDS) is discussed.

Adolescent↗
PubMedDate not supplied

An unusual amebic localization on the right hip.

We report the history of a 43-year-old man with a histopathologically confirmed invasive amebic abscess in his right hip. CT scan of the liver was normal. The amebic indirect hemagglutination (IHA) test was positive with a titer of 1/1,024. The patient developed acute renal failure and died within 48 h of admission with multiple organ failure due to sepsis.

Adult↗
PubMed1995

The relationship of water sources and other determinants to prevalence of intestinal protozoal infections in a rural community of Saudi Arabia.

A study was carried out in a rural area of Asir region in Southwest of Saudi Arabia where information on the types of domestic water supply and sociodemography in relation to intestinal protozoal infections were obtained from 1417 inhabitants (81.4% of the total) of nine villages. Stool samples were collected from the study population and examined for intestinal parasites. Overall, the prevalence rates of infection with the common water-borne parasites, Giardia lamblia and Entamoeba histolytica were 18.9% and 9.2% respectively, which were high compared to other endemic areas of the Kingdom. The sociodemographic factors including age, sex, degree of education, intrafamilial clustering and crowding index were found to be non significant determinants of both protozoal infections. The source of domestic water was the sole factor significantly associated with the high prevalence rates of infection in the community. This relationship was confirmed by multiple logistic regression analysis. A significantly high risk of contracting the infection with both parasites was observed among individuals who drank jar water (OR = 2.973, 95%CI:1.515-4.402 and OR = 2.831, 95%CI:1.414-3.915, for G. lamblia and E. histolytica respectively) or well water (OR = 2.153, 95%CI:1.211-3.913 and OR = 2.117, 95%CI:1.341-3.715, for G. lamblia and E. histolytica respectively). Those who used desalinated water for drinking seems to have the lowest degree of exposure to the risk of infection (OR = 0.689, 95%CI:0.501-0.849 and OR = 0.793, 95% CI:0.518-0.912, for G. lamblia and E. histolytica respectively). The results indicate that the use of improved water supply, including protection of community wells and domestic storage tanks, together with mandatory inspection measures during transportation and distribution of commercial water should reduce the rate of infection with the two protozoal parasites in this rural community.

Adolescent↗
PubMedDate not supplied

Parasitic infections in asymptomatic homosexual men: cost-effective screening.

The purpose of this study was to develop a cost-effective strategy for screening for enteric protozoan infections in homosexual men without gastrointestinal symptoms suggesting infection. One hundred and one homosexual men in Portland, Oregon, each submitted at least one unpurged stool sample; 91% submitted three samples each. Of these, 27% had Entamoeba histolytica, 61% had nonpathogenic protozoa with or without E. histolytica, 36% had a nonpathogen alone, and 3% had Giardia lamblia. Protozoan infection was highly associated with the practice of anilingus (p less than 0.005). Infection with E. histolytica correlated significantly with the presence of nonpathogenic protozoa (p less than 0.005). The following screening strategy was judged to be the most cost-effective: examine one sample first; if E. histolytica is found or if the sample is negative, no further investigation is required; if a nonpathogen is found, one additional sample should be obtained. This strategy had a sensitivity for E. histolytica of 85% and a cost of $136 per case detected.

Adult↗
PubMed2003

Amebiasis in the newborn.

Infestation with Entamoeba histolytica is especially common in areas with low socioeconomic status. Extra intestinal invasive involvement is more frequent in young children with significant mortality. This disease is rarely reported in the newborns. This 19-day-old newborn who was infected with orally given surgar solution is presented. He was successfully treated with omidazole.

Amebicides↗