<i>In vitro</i>adhesion assays for probiotics and their<i>in vivo</i>relevance: a review

Adhesion to the intestinal mucosa is one of the main selection criteria for probiotics. Selection of adhesive strains is performed in vitro. Little is known, however, as to how well in vitro adhesion correlates with in vivo adhesion; to date, this has not been systematically reviewed. Because the various adhesion models usually describe only one part of the intestinal mucosa, a combination of models may provide the best information. Incubation conditions affect the outcome of an adhesion assay and should be optimized for physiological relevance. The effects of digestion, the food matrix and the normal microbiota appear to have a significant influence, but have not been extensively investigated. Many factors interfere with the mucosal adhesion of probiotics, it is therefore difficult to extrapolate in vitro adhesion results reliably to the in vivo situation in humans. It is suggested that the relationship between in vitro and in vivo adhesion and the significance of adhesion for probiotic efficacy should be further investigated. In determining the in vivo importance of adhesion and the assumed relationship between in vitro and in vivo adhesion, adhesive and low-adhesive isogenic strains would appear to be the best tools.