Abstract:
Probiotics are live microorganisms that when administered in adequate amounts confer a health
benefit on the host by keeping their intestinal microflora in balance. Most probiotics are mainly
Lactic Acid Bacteria (LAB), including Latobacillus spp. and Bifidobacterium spp. Previous
studies showed that probiotic bacteria can \restore the gut flora and inhibit pathogens. Our study
aimed to isolate and characterize Bifidobacterium strains from local indigenous sources. This
study further investigated the antibacterial and cytotoxic activities of Bifidobacterium, isolates.
Duck and rice samples were used as sources for isolation of these bacteria. Identification of
bacterial strains was performed by biochemical testing and 16S rRNA gene sequencing.
Survival, adhesion and colonization were examined in gastrointestinal tract of mice. Agar well
diffusion method was used to assess the antimicrobial activity of isolates against STEC and
Shigella. Cytotoxic activities against cancerous cell lines were evaluated using MTT colometric
assay. Results of biochemical testing and 16S RNA sequencing revealed that isolates belong to
Bifidobacterium animalis. The results of the antibacterial testing showed that each strain of the
probiotic bacteria had varying activity against the pathogens under similar conditions. In
addition, our findings showed a significant cytotoxic activity against Huh-7 and HeLa cell lines.
Rifampicin-resistant colonies of B. Animalis strains were successfully re-isolated from the faecal
samples of treated mice. The similar results of colonization were achieved in the homogenated
samples of small intestine; large intestine and caecum of mice on the twenty eight day after
feeding with B. animalis Strains. The positive results of the study suggest that these B. animalis
strains may be useful as a probiotic candidate in healthcare and food industry.
