Amebiasis is an intestinal disease transmitted by the protist parasite, Entamoeba histolytica. Lactobacillus acidophilus is a common inhabitant of healthy human gut and a probiotic that has antimicrobial properties against a number of pathogenic bacteria, fungi, and parasites. The aim of this study was to investigate the amebicide activity of L. acidophilus and its mechanisms. For this purpose, E. histolytica and L. acidophilus were co-incubated and the parasite’s viability was determined by eosin dye exclusion. The level of ozidized proteins (OXs) in the parasite was determined by resin-assisted capture RAC (OX–RAC). Incubation with L. acidophilus for two hours reduced the viability of E. histolytica trophozoites by 50%. As a result of the interaction with catalase, an enzyme that degrades hydrogen peroxide (H2O2) to water and oxygen, this amebicide activity is lost, indicating that it is mediated by H2O2 produced by L. acidophilus. Redox proteomics shows that L. acidophilus triggers the oxidation of many essential amebic enzymes such as pyruvate: ferredoxin oxidoreductase, the lectin Gal/GalNAc, and cysteine proteases (CPs). Further, trophozoites of E. histolytica incubated with L. acidophilus show reduced binding to mammalian cells. These results support L. acidophilus as a prophylactic candidate against amebiasis.

The human protozoan parasite Entamoeba histolytica is responsible for amebiasis, a disease endemic to developing countries. E. histolytica trophozoites are released from the cysts to colonize the large intestine, where they primarily feed on bacterial cells. In these scenarios, bacterial cells form aggregates or structured communities too large for phagocytosis. Our results show that E. histolytica can degrade pre-established biofilms of Bacillus subtilis and Escherichia coli in a dose- and time-dependent manner. Surprisingly, trophozoites incubated with B. subtilis biofilm exhibit a unique transcriptome signature compared to those incubated with planktonic cells or without bacteria. Biofilm-induced genes include cysteine proteases (CPs), and the general inhibition of CPs by E64D or by the use of specific small-RNA (sRNA)-based RNA interference impairs the degradation of biofilms by E. histolytica. The degradation of B. subtilis extracellular matrix (ECM) protein TasA by CPs is associated with partial biofilm digestion and activation of the stress response in the interacting B. subtilis cells. The interaction with B. subtilis biofilms was also associated with lower levels of oxidoreductases. Oxidoreductase downregulation can be a readout of the embedding of E. histolytica trophozoites within the biofilm-produced extracellular matrix, reducing their exposure to oxidative stress (OS). Our results indicate that parasites may digest biofilms by a controlled mechanism of digestive exophagy as secretion of digestive enzymes as a conserved mechanism for biofilm degradation allows phagocytic digestion of biofilm cells. Furthermore, the partially digested biofilms can serve as an unexpected shield protecting parasites from oxidative environments and thereby may regulate the persistence and virulence of the parasite.

Amoebiasis is an intestinal disease transmitted by the protist parasite, Entamoeba histolytica, following the ingestion of contaminated food and water. In the colon, E. histolytica can phagocytose bacteria that are the main components of the microbial flora. Most infected individuals are asymptomatic but for unknown reasons, the parasite can become virulent and invasive, causes amebic dysentery, and migrates to the liver, where they cause hepatocellular damage. For the last few decades, it has become evident that E. histolytica virulence is directly linked to its interaction with the gut microbiota. Lactobacillus acidophilus is a common inhabitant of healthy human gut and a probiotic that present antimicrobial activity against many pathogenic bacteria, fungi and parasites. The purpose of this study was to examine the mechanisms behind the innate amebicide activity of L.acidophilus. We found that this activity is mediated by hydrogen peroxide (H2O2) produced by L. acidophilus. Redox proteomics shows that L. acidophilus triggers the oxidation of many essential amebic enzymes like pyruvate:ferredoxin oxidoreductase, the lectin Gal/GalNAc and cysteine proteases (CPs). Further, trophozoites of E.histolytica cultivated with L.acidophilus show reduced binding to mammalian cells. These results support L.acidophilus as a prophylactic candidate against amoebiasis.

Amebiasis is an intestinal disease transmitted by the protist parasite, Entamoeba histolytica. Lactobacillus acidophilus is a common inhabitant of healthy human gut and a probiotic that has antimicrobial properties against a number of pathogenic bacteria, fungi, and parasites. The aim of this study was to investigate the amebicide activity of L. acidophilus and its mechanisms. For this purpose E.histolytica and L.acidophilus were co-incubated and the parasite’s viability was determined by eosin dye exclusion. The level of ozidized proteins (OXs) in the parasite was determined by resin-assisted capture RAC (OX-RAC). Incubation with L.acidophilus for two hours reduced the viability of E.histolytica trophozoites by 50%. As a result of the interaction with catalase, an enzyme that degrades hydrogen peroxide (H2O2) to water and oxygen, this amebicide activity is lost, indicating that it is mediated by H2O2 produced by L.acidophilus. Redox proteomics shows that L. acidophilus triggers the oxidation of many essential amebic enzymes like pyruvate:ferredoxin oxidoreductase, the lectin Gal/GalNAc and cysteine proteases (CPs). Further, trophozoites of E.histolytica incubated with L.acidophilus show reduced binding to mammalian cells. These results support L.acidophilus as a prophylactic candidate against amebiasis.