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

Highlights•Ex-vivo approaches to assess bacterial adhesion in the intestinal tract, considering the complexicity of the mucus.•Viable bacteria–mucus adhesion index, a new concept of bacterial adhesion where the viability of bacteria is considered.•Strong impact of the morphological attributes of bacteria on their adhesion potential to the intestinal surface.•Positive effect of bacterial aggregation on their adhesion efficiency to extracellular matrices in the gut.AbstractRecent 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 Escherichia coli, Lactiplantibacillus plantarum, Faecalibacterium duncaniae, Bifidobacterium longum, and Bifidobacterium longum str. infantis were selected for the investigation. In that context, higher adhesion to mucus was demonstrated by E. coli, L. plantarum, and B. infantis, 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.