Isolation and Potential Probiotic Characterization of Lactic Acid Bacteria from an Ethnic Fermented Beverage having Antibacterial Activity against Human Pathogen Entamoeba histolytica

Background

Amoebiasis, caused by the human pathogen Entamoeba histolytica is one of the most common parasitic diseases. The existing anti-amoebic drugs show significant side effects in humans. Therefore, for effective control of this parasite, an alternative strategy is required. Microorganisms having probiotic potential are gaining global importance due to their health-promoting effects along with the safety aspects. Therefore, the present study aimed to isolate new lactic acid bacterial strains having anti-amoebic activity as well as probiotic potential from a traditional fermented beverage consumed by an Indian tribal community.

Materials and Methods

Twenty bacterial isolates have been selected based on their tolerance ability towards acid and bile salt. Their biofunctional aspects and anti-amoebic potential are studied. The most potential one was chosen through heatmap visualization and principal component analysis based on probiotic attributes. Finally, the opted isolate was studied for its in vivo safety evaluation using mouse model.

Results and Discussion

The isolates were found as Gram positive, catalase negative and able to ferment different carbohydrates. They showed significant killing activity against Entamoeba histolytica. They were found to have a high tolerance to gastrointestinal stresses, antioxidant activity, sensitivity to various antibiotics, high auto-aggregation activity (up to 28.78%), cell-surface hydrophobicity (up to 78.75%) and antibacterial activity. Their negative activity in gelatin hydrolysis and haemolysis assay indicates that they are safe. From 16s rDNA sequencing, they were found to be Limosilactobacillus sp. Among the isolates, B-51 was considered as the best probiotic strain by heatmap visualization and principal component analysis. Importantly, the strain B-51 showed beneficial effects in mice when supplemented through oral gavage.

Conclusion

The isolated strains from rice fermented beverage showed anti-amoebic activity along with interesting probiotic traits. The in vivo study findings of the best one proved its potential for therapeutic application in humans.