Adhesion of selected Bifidobacterium strains to human intestinal mucus and the role of adhesion in enteropathogen exclusion

The ability of potential probiotic strains to adhere to the intestinal mucosa and exclude and displace pathogens is of utmost importance for therapeutic manipulation of the enteric microbiota. The ability of seven selected human bifidobacterial strains and five human enteropathogenic strains to adhere to human intestinal mucus was analyzed and compared with that of four strains isolated from chicken intestines. The adhesion of the bifidobacterial strains ranged from 3 to 16% depending on the strain. Bifidobacterium strains of animal origin adhered significantly better than did strains of human origin. Of the pathogenic bacteria, Escherichia coli NCTC 8603 had the highest adhesion value (20%), Salmonella Typhimurium ATCC 29631, Enterobacter sakazakii ATCC 29544, and Clostridium difficile ATCC 9689 had adhesion values ranging from 10 to 15%, and Listeria monocytogenes ATCC 15313 had the lowest adhesive value (3%). The ability of these bifidobacteria to inhibit pathogen adhesion and to displace pathogens previously adhering to mucus was also tested. The inhibition of pathogens adhesion by these bifidobacterial strains was variable and clearly strain dependent. In general, bifidobacterial strains of animal origin were better able to inhibit and displace pathogens than were human strains. Preliminary characterization of bacterial adhesion was accomplished using different pretreatments to explore adhesion mechanisms. The results indicate that different molecules are implicated in the adhesion of bifidobacteria to the human intestinal mucus, constituting a multifactorial process.