We isolated several strains of human and animal origin, focusing on the genera Lactobacillus and Bifidobacterium. Samples of cow colostrum, feces and saliva of calves and piglets, and infant feces were acquired, bacterial strains were isolated and identified, and twenty strains of lactobacilli and bifidobacteria were shortlisted for further in vitro analysis of adhesion capacity to human cells, surface hydrophobicity, and auto-aggregation. Adhesion capacity was evaluated using a mixture of Caco-2 and HT-29-MTX cells and hydrophobicity was measured using the microbial adhesion to the hydrocarbon method. Lactobacillus reuteri was the most frequently isolated species, followed by L. casei subsp. paracasei and L. gasseri; all strains were isolated from infant feces. Bifidobacteria were represented by the species B. longum (infant feces), and B. thermophilum and B. pseudolongum (calves, piglets). All twenty strains showed good adhesion capacities to the mixed cell culture (17.7–37.2%), particularly, L. reuteri isolates K7 and K14 (37.2% and 35.5%, respectively). In hydrophobicity and auto-aggregation assays, strain-specific differences irrespective of the origin or taxonomic group were observed. Hydrophobicity values varied considerably (from 6.1% to 87.4%), whereas auto-aggregation ability ranged from 21.7% to 69.7%. No relation was observed between hydrophobicity and adhesion capacity; instead, auto-aggregation was apparently related with adhesion.

The ability of bacteria to adhere to the intestinal mucosa is a critical property necessary for the long-term colonization of the intestinal tract. This ability can be highly sensitive to the presence of prebiotics. However, limited data are available in this respect for beneficial bacteria such as probiotics or resident gut microbiota. We previously demonstrated that the presence of prebiotics may decrease adherence in several pre- and probiotic combinations. Thus, characterizing the interactions between numerous combinations involving different classes of pre- and probiotics can be crucial in identifying new synbiotics. Accordingly, here, we extend our prior analyses to evaluate the adhesion of five lactobacilli, six bifidobacteria, and one probiotic Escherichia coli strains, as commercial probiotics or promising probiotic candidates, together with the cariogenic Bifidobacterium dentium strain. As an in vitro intestinal mucosa model, Caco-2 and mucin-secreting HT29-MTX cells were co-cultured at 9:1 in the presence or absence of prebiotics. Commercial inulin-type fructooligosaccharide prebiotics Orafti® GR, Orafti® P95, and galactooligosaccharide-based prebiotic formula Vivinal®, including purified human milk oligosaccharides (HMOs) were added into the cultivation media as the sole sugar source (2.5% each). Adherence was tested using microtiter plates and was evaluated as the percentage of fluorescently labeled bacteria present in the wells after three washes. Consistent prebiotics-mediated enhanced adherence was observed only for the commercial probiotic strain E. coli O83. For the remaining strains, the presence of HMO or prebiotics Orafti® P95 or Orafti® GR decreased adherence, reaching statistical significance (p < 0.05) for three of out of eight (HMO) or five of out of 11 strains tested, respectively. Conversely, Vivinal® enhanced adhesion in six out of the 12 strains tested, and notably, it significantly attenuated the adherence of the cariogenic Bifidobacterium dentium Culture Collection of Dairy Microorganisms (CCDM) 318. To our knowledge, this represents the first report on the influence of commercial prebiotics and HMOs on the adhesion of the cariogenic Bifidobacterium sp. Vivinal® seems to be a promising prebiotic to be used in the formulation of synbiotics, supporting the adhesion of a wide range of probiotics, especially the strains B. bifidum BBV and BBM and the probiotic Escherichia coli O83.