Comparison of in vitro models to study bacterial adhesion to the intestinal epithelium

To evaluate the adhesion ability of intestinal bacteria to different in vitro models of intestinal epithelia, and to estimate the suitability of these models and the type of interactions involved. The adhesion of probiotic (Lactobacillus rhamnosus GG and Bifidobacterium animalis subsp. lactis Bb12), commensal (B. animalis IATA-A2 and B. bifidum IATA-ES2) and potentially pathogenic bacteria (E. coli and L. monocytogenes) was determined. The adhesion models used were polycarbonate-well plates, with or without mucin, and different configurations of Caco-2 and/or HT29-MTX cell cultures. All bacteria adhered to wells without mucin (2·6-27·3%), the values being highly variable depending on the bacterial strain. Adhesion percentages of potentially probiotic bacteria to Caco-2 cultures were remarkably lower (P < 0·05) than those to mucin, and more similar to those of pathogenic strains. The lowest adhesion of different bacterial strains was detected on HT29-MTX (0·5-2·3%) cultures and Caco-2/HT29-MTX (0·6-3·2%) cocultures, while these values were increased in Caco-2 cultures plus mucin. The results suggested that bacterial strains exhibit different capacities to adhere to cellular components and several types of mucin present in different models, showing preferences for intestinal MUC2. The use of Caco-2 cells monolayer plus mucin (type II) better approaches the physiological characteristics of in vivo situation, providing a reliable and suitable in vitro model to evaluate bacterial adhesion.