Human Amebiasis: Breaking the Paradigm?

Abstract

For over 30 years it has been established that the Entamoeba histolytica protozoan included two biologically and genetically different species, one with a pathogenic phenotype called E. histolytica and the other with a non-pathogenic phenotype called Entamoeba dispar. Both of these amoebae species can infect humans. E. histolytica has been considered as a potential pathogen that can cause serious damage to the large intestine (colitis, dysentery) and other extraintestinal organs, mainly the liver (amebic liver abscess), whereas E. dispar is a species that interacts with humans in a commensal relationship, causing no symptoms or any tissue damage. This paradigm, however, should be reconsidered or re-evaluated. In the present work, we report the detection and genotyping of E. dispar sequences of DNA obtained from patients with amebic liver abscesses, including the genotyping of an isolate obtained from a Brazilian patient with a clinical diagnosis of intestinal amebiasis that was previously characterized as an E. dispar species. The genetic diversity and phylogenetic analysis performed by our group has shown the existence of several different genotypes of E. dispar that can be associated to, or be potentiality responsible for intestinal or liver tissue damage, similar to that observed with E. histolytica.

Analysis of the Bacterial Diversity in Liver Abscess: Differences Between Pyogenic and Amebic Abscesses

“…Indeed, the spectrum of outcomes of these infections could be related to the bacterial/protozoan density ratio. In a previous study, 27 we hypothesized that the size of intestinal amebic ulcers and the local inflammatory response permits the exit of E. histolytica trophozoites and intestinal bacteria, some of which enter the phagocytic vacuoles of trophozoites. 11,47,48 Our current results agree with our previous hypothesis and may explain the diversity of disease outcomes.…”

“…20,21 In this scenario, almost all pathogenic enterobacteria can be cultured in the laboratory, [22][23][24][25] in contrast to the intestinal microbiota, which generally includes nonculturable bacteria. 26 Evidence of coinfections with both species of Entamoeba (E. histolytica and Entamoeba dispar) has been reported in patients with ALA. 27 Of note, the molecular characterization of E. dispar in a patient with enteritis was recently reported in Italy. 28 Furthermore, some patients with ALA present with mixed hepatic abscesses that are coinfected with pyogenic bacteria.…”

Cutaneous Amebiasis: The Importance of Molecular Diagnosis of an Emerging Parasitic Disease

“…Previously, our group reported cases of amoebic liver abscesses where the presence of both E. histolytica and E. dispar infection was demonstrated by PCR using different molecular markers. 32 Coincidentally, the amoebic lesions in these patients were also co-infected by pyogenic bacteria, Enterobacter cloacae and Staphylococcus aureus in patient 1, and Escherichia coli in patient 2. This outcome was similar to the case of pyogenic and mixed liver abscess (amoebic-pyogenic) reported previously.…”

“…This outcome was similar to the case of pyogenic and mixed liver abscess (amoebic-pyogenic) reported previously. 32 We propose that the pathogenic behavior of Entamoeba species in human infection could be potentiated by the co-infection with bacteria.…”

An Orthology-Based Analysis of Pathogenic Protozoa Impacting Global Health: An Improved Comparative Genomics Approach with Prokaryotes and Model Eukaryote Orthologs

“…Resistance to current anti-malarial drugs, such as chloroquinine, has already been reported (Hastings et al, 2002). E. histolytica is the causative agent of human amebiasis, a cosmopolitan disease whose most common clinical forms are amoebic colitis and amoebic liver abscess (Ximénes et al, 2010).…”