Axenic culture of Entamoeba histolytica alters its ability to interact with pathogenic bacteria and leads to loss of virulence and pathogenicity.

Entamoeba histolytica is an anaerobic eukaryotic protozoan capable of infecting humans and causing amoebiasis, a disease responsible for approximately 50 million cases and an estimated 100,000 deaths annually worldwide. The virulence of Entamoeba histolytica trophozoites and their ability to cause amoebic colitis and hepatic abscesses in the host involve various molecules, such as a specific lectin that recognizes galactose and N-acetylgalactosamine residues, cysteine proteinases, and amoebapores. To determine whether axenization of the Entamoeba histolytica strain affects its ability to interact with and respond to the presence of other microorganisms, we cultured trophozoites of an Entamoeba histolytica EGG strain in both xenic and axenic media. We then associated them with Salmonella typhimurium and evaluated the expression of virulence factors by real-time PCR. Subsequently, we infected rats to assess whether the Enatmoeba histolytica EGG strain cultured under xenic and axenic conditions exhibited differences in pathogenicity. This study showed that the absence of bacterial microbiota in axenic culture led to a reduced capacity to produce virulence factors in vitro, even when stimulated with Salmonella typhimurium. Furthermore, in vivo analysis revealed that axenic culture altered the parasite's behavior by reducing its ability to produce intestinal lesions, even in a co-infection setting. We suggest that the expression profiles of virulence genes are influenced by continuous environmental stress and that the presence of microbiota in xenic cultures of Enatmoeba histolytica contributes to such stress and supports the maintenance of virulence gene expression.