Zymodemes of Entamoeba histolytica isolated in the Amazon and the north-east of Brazil

The Stool Examination Reports Amoeba Cysts: Should You Treat in the Face of over Diagnosis and Lack of Specificity of Light Microscopy?

Amoebiasis is a common clinical diagnosis in tropical settings and clinicians continue to treat asymptomatic carriers diagnosed by light microscopy. A minority of carriers, however, are infected with Entamoeba histolytica and the remaining with the non-pathogenic Entamoeba dispar. We compared the diagnostic results of 298 asymptomatic residents of Aracaju, Brazil, obtained by different diagnostic methods, and ascertained their clinical symptoms, to highlight the implications for practitioners. Fifty-eight (19.4%) specimens were amoebae positive by microscopy. Of these, 38 (13%) were E. histolytica IE. dispar enzyme-linked immunosorbent assay (ELISA) positive and 4 (1%) E. histolytica ELISA positive. The frequent use of anti-amoebic treatment on the basis of non-specific symptoms and the findings of light microscopy tests is not justified. Methods for the specific diagnosis of E. histolytica infection for developing countries are urgently needed.

[Occurrence of Entamoeba histolytica/Entamoeba dispar in ambulatory patients of Recife, PE]

The objective this study was to determine the occurrence of the species Entamoeba histolytica/Entamoeba díspar in clinical samples of ambulatory patients in Pernambuco. A specific assay for Entamoeba histolytica was used in this study, which identified no positive fecal samples among the 213 patients. These results confirm that E. dispar is the dominant species in Pernambuco State.

Genetic characterization of Entamoeba dispar isolates in Northeast Brazil

The genetic variability of Entamoeba dispar strains was investigated in 39 positive isolates on a survey of 1783 individuals from two different cities of Northeast Brazil (Recife and Macaparana) using two polymorphic species-specific loci (loci 1-2 and 5-6). A combinatory clustering analysis revealed no geographical correlation and remarkable genetic polymorphism among all the isolates examined. Nevertheless, a comparison of the frequency of eight individual PCR products, shared by both Recife and Macaparana populations, for the two loci, showed that only one product of locus 5-6 was significantly different between the two cities. These results suggested that the Macaparana population is infected by similar strains and that locus 5-6 shows potential in assaying questions related to the molecular epidemiology of this region.

Entamoeba histolytica and Entamoeba dispar infections as detected by monoclonal antibody in an urban slum in Fortaleza, Northeastern Brazil

In this study the authors used the Elisa-based antigen detection tests that distinguish E. histolytica from E. dispar to examine the prevalence of E. histolytica infection in individuals from an urban slum in Fortaleza, Northeastern, Brazil. This test has a sensitivity and specificity that is comparable to PCR and isoenzyme analysis, which is the gold standard. Single stools samples were obtained from 735 individuals. The prevalence of E. histolytica infection was 14.9% (110/735) and 25.4%(187/735) for E. dispar-E. histolytica complex. The most affected age group for E. histolytica /E. histolytica-E. dispar infection was the 1-5 year olds but there was no remarkable decrease with age. There was no significant difference in colonization rates between males and females. The results from this survey demonstrate that E. histolytica is highly prevalent in the Community studied. Furthermore, it offers promise for the antigen detection test as a sensitive and technically simple tool for detecting E. histolytica infection in the field.

Isoenzyme profile as parameter to differentiate pathogenic strains of Entamoeba histolytica in Brazil

The isoenzyme profiles (IP) of 33 strains of Entamoeba histolytica isolated from patients and carriers of two regions in Brazil (Amazonia and Southeast) were determined. The enzymes phosphoglucomutase, glucose-phosphate isomerase, hexokinase and malic enzyme were considered. IP of the strains was correlated with culture conditions, time of maintenance in laboratory and clinical history of patients. The strains were maintained under polyxenic, monoxenic and axenic culture conditions: 27 polyxenic, 1 polyxenic and monoxenic, 1 polyxenic, monoxenic and axenic and 4 axenic only. The patients were symptomatic and asymptomatic. The symptomatic patients presented either non dysenteric (NDC) or dysenteric colitis (DC), associated or not with hepatic abscess (HA). One patient presented anal amoeboma (AM). The analysis of IP for isolates maintained in polyxenic culture showed non pathogenic IP (I) for strains from carriers and patients with NDC, while the strains isolated from patients presenting DC, HA and AM resulted in isolates II or XIX pathogenic IP. This parameter was not able to differentiate strains from carriers from symptomatic patients when these strains were found in axenic or monoxenic culture. All these strains displayed pathogenic IP (II), demonstrating the inability of this parameter to classifying for virulence since it showed identical IP for strains isolated from carriers or symptomatic patients.

Prevalence and pathogenicity of Entamoeba histolytica in three different regions of Pernambuco, northeast Brazil

Parasitological examinations were carried out on 663 individuals of three different cities of Pernambuco State, Northeastern Brazil: Recife, Palmares and Bodocó. The population from a drought area of Pernambuco State, Bodocó, was investigated for amoebiasis and compared with Recife, metropolitan city (about 1.3 million of inhabitants) and another inland community, Palmares, located inside of the sugar-cane plantation region of the State. No evidence of invasive strains of E. histolytica were found in these inhabitants, provided that the isolated zymodemes I, III, IV, VIII, IX, X, XVII and XVIII are recognized as nonpathogenic strains of E. histolytica. Furthermore, the prevalence of intestinal helminths and other protozoan infections showed that these individuals are infected by other agents responsible for diarrhoeal diseases.

Amebiasis

Entamoeba histolytica, the causative agent of amebiasis, was first described in 1875. Although a large number of people throughout the world are infected with this organism, only a small percentage will develop clinical symptoms. Morbidity and mortality due to E. histolytica vary from area to area and person to person. Recent findings have suggested that there are pathogenic and nonpathogenic strains of E. histolytica that can be differentiated by isoenzyme (zymodeme) analysis, monoclonal antibodies, and DNA probes. Whether pathogenicity is a genotypic trait or can be changed by environmental influences has not been resolved. Exchange of genetic material between strains of amebae can influence zymodeme patterns. Currently, detection of E. histolytica infections depends on examinations for ova and parasites and on serologic tests; however, the development of monoclonal antibodies and DNA probes specific for pathogenic zymodemes may be beneficial for clinical laboratory testing and therapeutic decisions when approved tests become available. A better understanding of the mechanisms of pathogenicity at the molecular level is evolving and should promote the development of vaccines and better target selection for therapeutic agents.

Analysis of pathogenicity by restriction-endonuclease digestion of amplified genomic DNA of Entamoeba histolytica isolated in Pernambuco, Brazil

The pathogenicity of 47 strains of Entamoeba histolytica isolated in Pernambuco, Brazil, was examined using the polymerase chain reaction (PCR) followed by restriction-endonuclease digestion. Electrophoretic patterns of PCR products digested with HinfI revealed that all strains were nonpathogenic. The results were entirely in accord with phenotypic properties such as isoenzyme patterns and the failure to bind a pathogenic-isolate-specific monoclonal antibody. When the sensitivity of PCR was examined, amplified products could be detected from template DNA equivalent to five trophozoites. These observations indicate that PCR amplification of genomic DNA and subsequent restriction-enzyme digestion is a useful strategy for obtaining a sensitive and accurate diagnosis. The present study also demonstrates that nonpathogenic strains of E. histolytica predominate in northeastern Brazil.