Inhibition of Salmonella typhimurium by Bifidobacterium breve

Abstract:

[Background] Salmonella typhimurium is one of the major intestinal pathogens. The use of probiotics to treat intestinal pathogen infection has becoming a new, green micro-ecological method. [Objective] Investigate the antibacterial activity and mechanism of the cell-free supernatant (CFS) of Bifidobacterium breve on S. typhimurium in vitro. [Methods] The microdilution method was used to detect the minimum inhibitory concentration (MIC) and sub-inhibitory concentration (SIC) of YH68 CFS against S. typhimurium. The antibacterial mechanism of YH68 CFS against S. typhimurium was investigated from the changes of cell morphology, cell membrane permeability, membrane integrity and virulence gene expression of S. typhimurium. The adhesion and invasion of S. typhimurium to HT29 cells were also studied. [Results] YH68 CFS (3×109 CFU/mL) has a good inhibitory effect on S. typhimurium, and the diameter of the inhibition zone is 22.27±0.44 mm. When YH68 CFS was at MIC concentration (250 μL/mL), its mechanism of action against S. typhimurium was to increase the membrane permeability, destroy its integrity, form the cell membrane pores, and ultimately achieve antibacterial purposes. However, YH68 CFS did not affect the growth of S. typhimurium at the concentration of SIC (62.5 μL/mL), but it could still inhibit the adhesion and invasion of intestinal epithelial cells by down-regulating the expression of its virulence genes. [Conclusion] Bifidobacterium breve YH68 has a good antibacterial effect against S. typhimurium and could be used as a potential probiotic for clinical treatment of Salmonella infection.