Ex-vivo investigation of probiotic bacterial adhesion to the intestinal mucus

Recent research has promoted considerable interest in the potential health benefits of the new generation of probiotics. Despite the abundance of probiotic supplements, their adhesion and thereby colonization in the intestinal tract of the host, a determining factor of probiotic efficacy, remains questionable. Indeed, the gastrointestinal tract, a multi-component and complex system, obscures the comprehensive understanding of the probiotic adhesion mechanism. This study aimed to investigate the adhesion capacity of probiotic bacteria using two ex-vivo approaches that were specifically developed to investigate the bacteria-mucus agglomeration and the viable adhesion to intestinal mucus. Five probiotic bacterial strains including <i>Escherichia coli</i>, <i>Lactiplantibacillus plantarum</i>, <i>Faecalibacterium duncaniae</i>, <i>Bifidobacterium longum</i>, and <i>Bifidobacterium longum</i> str. <i>infantis</i> were selected for the investigation. In that context, higher adhesion to mucus was demonstrated by <i>E. coli</i>, <i>L. plantarum</i>, and <i>B. infantis</i>, emphasizing strain-specific differences. While total agglomeration capacity ranged from 8 % to 82 %, actual viable adhesion to mucus remained rather low (0.6 %-2.9 %). SEM images revealed that morphological characteristics, chain and/or cluster forming ability, as well as the presence of surface exopolysaccharides, might have an impact on bacterial adhesion. This study contributes knowledge on probiotic adhesion as well as simple and effective ex-vivo approaches to investigate the bacterial adhesion to the intestinal mucus, which is prerequisite for further colonization in the gut of the host.