Three types of assay were performed to ascertain the ability of the probiotic strain to block adherence of E. coli to Caco-2 cells: blockage by exclusion, by competition or by displacement, as described previously by Peres et al. (2014). Inhibition of pathogen adhesion was quantified by comparing viable counts of adhered bacteria to those in control experiments run without the probiotic bacteria. An adhesion index was calculated, as the number of bacteria attached per 100 epithelial cells, and its mean and standard deviation were duly computed.
To evaluate the synergy of olive bioactive phytochemicals and lactobacilli upon adherence of E. coli, Caco-2 monolayers were cultured with RPMIm added with either OL or HT. The control assay consisted on assessment of adhesion ability in the absence of OL and HT.