The Interplay between Entamoeba and Enteropathogenic Bacteria Modulates Epithelial Cell Damage

Abstract

BackgroundMixed intestinal infections with Entamoeba histolytica, Entamoeba dispar and bacteria with exacerbated manifestations of disease are common in regions where amoebiasis is endemic. However, amoeba–bacteria interactions remain largely unexamined.MethodologyTrophozoites of E. histolytica and E. dispar were co-cultured with enteropathogenic bacteria strains Escherichia coli (EPEC), Shigella dysenteriae and a commensal Escherichia coli. Amoebae that phagocytosed bacteria were tested for a cytopathic effect on epithelial cell monolayers. Cysteine proteinase activity, adhesion and cell surface concentration of Gal/GalNAc lectin were analyzed in amoebae showing increased virulence. Structural and functional changes and induction of IL-8 expression were determined in epithelial cells before and after exposure to bacteria. Chemotaxis of amoebae and neutrophils to human IL-8 and conditioned culture media from epithelial cells exposed to bacteria was quantified.Principal Findings E. histolytica digested phagocytosed bacteria, although S. dysenteriae retained 70% viability after ingestion. Phagocytosis of pathogenic bacteria augmented the cytopathic effect of E. histolytica and increased expression of Gal/GalNAc lectin on the amoebic surface and increased cysteine proteinase activity. E. dispar remained avirulent. Adhesion of amoebae and damage to cells exposed to bacteria were increased. Additional increases were observed if amoebae had phagocytosed bacteria. Co-culture of epithelial cells with enteropathogenic bacteria disrupted monolayer permeability and induced expression of IL-8. Media from these co-cultures and human recombinant IL-8 were similarly chemotactic for neutrophils and E. histolytica. ConclusionsEpithelial monolayers exposed to enteropathogenic bacteria become more susceptible to E. histolytica damage. At the same time, phagocytosis of pathogenic bacteria by amoebae further increased epithelial cell damage.SignificanceThe in vitro system presented here provides evidence that the Entamoeba/enteropathogenic bacteria interplay modulates epithelial cell responses to the pathogens. In mixed intestinal infections, where such interactions are possible, they could influence the outcome of disease. The results offer insights to continue research on this phenomenon.

Diarrheagenic Escherichia coli in sub-Saharan Africa: Status, Uncertainties and Necessities

“…Interactions between different pathogens have not been commonly studied but two reports suggest that mixed infections that include diarrheagenic E. coli may be exceptionally deleterious [255,256].…”

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

“…8,9 In addition, it has been demonstrated that amebas can either ingest bacteria or keep them attached to the amebic membrane in a mutualistic interaction that allows the transfer of genetic information to the Entamoeba parasite. 2,3,10,11 Other studies have shown that in the absence of bacteria, E. histolytica does not express virulence factor-associated genes. Long-term axenic cultures of E. histolytica HM1:IMSS show loss of virulence in both in vitro (cytopathic and cytotoxic effects in cell cultures) and in vivo models of infection (amebic liver abscess [ALA] in hamsters).…”

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“…Modulating factors that regulate the cell cycle 25 , composition of the culture media and bacterial flora 26,27 has not yet successfully yielded infective cysts of E. histolytica. Despite carrying out the in vitro excystation of E. histolytica, factors that induce this process remain poorly understood.…”