Amebiasis is one of the most frequent protozoan infections of man, because an estimated 10% of the world population is affected (1). The disease is caused by Entamoeba histolytica, the only Entamoeba known to be pathogenic for humans. The motile form or trophozoite can live in the intestinal lumen as a harmless commensal, but occasionally, and for unknown reasons, it can invade the colonic mucosa giving rise to amebic dysentery and subsequently to liver abscesses (2). In addition to E. histolytica, nonpathogenic Entamoeba species like Entamoeba coli, and Entamoeba hartmanni may inhabit the human intestine. The reasons for the different behavior of pathogenic and nonpathogenic Entamoeba are not known.Basic structural or biochemical differences which could account for the erratic invasive behavior of Entamoeba have not been found (3, 4). However, pathogenic strains of E. histolytica differ from strains isolated from asymptomatic carriers and other nonpathogenic Entamoeba in certain surface properties, such as the susceptibility to agglutinate with the plant lectin concanavalin A, and the lack of surface charge (5, 6).Another surface property characteristic of Entamoeba is the ability to phagocytize a variety of particulate material including starch grains, bacteria, various protozoa, inert polyestyrene beads, and erythrocytes (7-16). More than 100 yr ago Lesh (LiSsch) (17) demonstrated that amebas in stool samples from human dysentery contained erythrocytes. Since then, it has been claimed repeatedly that invasive strains of E. histolytica are the only intestinal amebas of humans able to ingest erythrocytes. Erythrophagocytosis has been traditionally considered as one of the most important criteria in identifying pathogenic E. histolytica trophozoites, as a perusal of texts on human protozoology will reveal (1, 18-25) with few exceptions (2).In view of the importance given to the presence of ingested erythrocytes for the identification of invasive E. histolytica, the lack of systematic comparative studies is striking. On one hand, Entamoeba other than E. histolytica have occasionally been shown to engulf erythrocytes both in vivo and in vitro (16,26,27). On the other hand, studies on E. moshkovskii (the only free-living Entamoeba known) are contradictory, because it has been reported to be able (28) or unable (29) to phagocytize erythrocytes. Shaffer and Ansfield (30) studied the erythrophagocytosis in a number of E. histolytica strains without specifying their virulence.In continuation of our studies on the surface properties of Entamoebae (5, 6) we have

In four cities of Venezuela a study was carried out to evaluate the epidemiological, clinical, and etiological characteristics of acute diarrhea in children under 5 years of age. The study was done between June 1993 and May 1995 and involved children who were seen in a hospital, 2,552 with diarrhea and 793 controls. The Fisher exact test was used for the statistical analysis of the results. Rotaviruses were the most important agents, both in terms of their frequency (30%) and their association with dehydration (58%). Following in importance were Campylobacter spp. (13%) and Escherichia coli classical O serogroups (9%), but their association with diarrhea was only statistically significant among children less than 3 months old, a fact that is particularly important from the standpoint of treatment. The importance of age was confirmed as a determining factor in the prevalence and severity of diarrhea.

Free-living amoebae of Acanthamoeba genus are opportunistic pathogens distributed worldwide. Strains included in this genus are causative agents of a fatal encephalitis and a sight-threating keratitis in humans and other animals. In this study, 550 clinical samples which were collected between 1984 and 2014 from different patients with suspected infections due to Acanthamoeba were initially screened for the presence of this amoebic genus at the Laboratorio de Amibiasis-Escuela de Bioanálisis at the Universidad Central de Venezuela. Samples were cultured in 2% Non-Nutrient agar plates seeded with a layer of heat killed Escherichia coli. From the 550 clinical samples included in this study, 18 of them were positive for Acanthamoeba genus after culture identification. Moreover, positive samples were confirmed after amplification of the Diagnostic Fragment 3 (DF3) of the Acanthamoeba18S rDNA genus and sequencing was carried out in order to genotype the isolated strains of Acanthamoeba. Furthermore, the pathogenic potential of the strains was checked by performing thermotolerance and osmotolerance assays. Sequencing of the DF3 region resulted in the identification of genotype T4 in all the isolated strains. Moreover, most isolates were thermotolerant or both thermotolerant and osmotolerant and thus were classified as potentially pathogenic strains. To the best of our knowledge, this is the first report on the molecular characterization at the genotype level of Acanthamoeba strains in Venezuela.

Human anti-Entamoeba histolytica immunoglobulin was used to detect Entamoeba histolytica in 74 positive samples from several different sources, using an indirect immunoperoxidase method. In 73 samples, the protozoan was easily identified. Trophozoites and cysts of all cultured Entamoeba strains examined were strongly stained, and as few as 3 trophozoites per microscope slide could be detected. In addition, 51 negative control samples were also tested and non-specific reactions were not observed. These preliminary results show that this method is both sensitive and specific, and can easily detect trophozoites and cysts of different E. histolytica strains.