Bacteriocin production and adhesion properties as mechanisms for the anti-listerial activity of 423 and ST4SA.

Probiotics play an important role in maintaining a healthy and stable intestinal microbiota, primarily by preventing infection. Probiotic lactic acid bacteria (LAB) are known to be inhibitory to many bacterial enteric pathogens, including antibiotic-resistant strains. Whilst the positive role that probiotics have on human physiology, specifically in the treatment or prevention of specific infectious diseases of the gastro-intestinal tract (GIT) is known, the precise mechanistic basis of these effects remains a major research goal. In this study, molecular evidence to underpin the protective and anti-listerial effect of 423 and ST4SA against orally administered EGDe in the GIT of mice is provided. Bacteriocins plantaricin 423 and mundticin ST4SA, produced by 423 and ST4SA, respectively, inhibited the growth of and . Bacteriocin-negative mutants of 423 and ST4SA failed to exclude EGDe from the gastrointestinal tract (GIT) of mice. Furthermore, 423 and ST4SA failed to inhibit recombinant strains of EGDe that expressed the immunity proteins of the two bacteriocins. These results confirmed that bacteriocins plantaricin 423 and mundticin ST4SA acted as anti-infective mediators . Compared to wild type strains, mutants of 423 and ST4SA, in which the adhesion genes were knocked out, were less effective in the exclusion of EGDe from the GIT of mice. This work demonstrates the importance of bacteriocin and adhesion genes as probiotic anti-infective mechanisms.