Isolation and characterization of Bifidobacterium animalis strains and evaluation of their antibacterial and cytotoxic activities

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.