Screening, Isolation, Characterization and Evaluation of Safety of Potential Probiotic Strains Isolated from Indigenous Rice Sources.

Abstract

Probiotics are living microorganisms which can change the microbiota of the host and ultimately have beneficial effects on the health of the host when present in significant numbers. Their applications are very diverse as they are used in foods, for the treatment and prevention of many diseases, maintaining the health of an individual and currently their applications as therapeutics are being discovered. The aim of my study was to isolate potential probiotics from indigenous sources, evaluate their characteristics and perform their safety assessment. Different varieties of indigenous rice were taken as source for the isolation of bacteria. Identification of the isolated strains was performed by various biochemical tests and 16S rRNA sequencing. The safety of isolated strains was assessed on wistar rats for 10 weeks including survival, adhesion, and colonization of the strains in gastrointestinal tract of rats. Antibacterial activity of isolated strains against five pathogenic strains namely Shiga toxin producing Escherichia coli, Enterococcus faecalis, Salmonella enterica, Pseudomonas aeruginosa and Klebsiella Pneumoniae was performed by well diffusion assay. Three strains were isolated whose biochemical testing and sequencing results revealed they were Enterococcus faecium. No significant antagonism was seen against K. Pneumoniae and P. aeruginosa whereas significant results were obtained against STEC, E. faecalis and S. enterica. Strains survived the GIT tract as they were re-isolated as rifampicin resistant colonies in the fecal samples of rats. They were able to adhere and colonize small intestine; large intestine and caecum of rats. The rats were gaining weight and no symptoms of disease were shown ensuring the safety of the strains. The results of the study suggest that these E. faecium strains can be used as potential probiotic strains.