Inhibition of adhesion of uropathogenic Escherichia coli bacteria to uroepithelial cells by extracts from cranberry.

Cranberry extract has been reported as a therapeutic agent, mainly in urinary tract infections due to its anti-adhesive capacity. In order to compare the effects of proanthocyanidin (procyanidin) (PAC)-standardized cranberry extracts and commercial PAC A2, we first investigated the presence of genes encoding known adhesins on 13 strains of uropathogenic strains coming from patients with cystisis. After this characterization, the anti-adhesive effects of PAC A2 were assayed on selected uropathogenic Escherichia coli strains before testing cranberry extracts. Before checking inhibitory effect on bacterial adhesion to cells, we showed that neither PAC A2 or three cranberry extracts (A, B, and C) specifically inhibited the growth and did not supply any potential nutrient to E. coli strains, including the unrelated control strain. PAC A2 exhibited an inhibitory effect on the adhesion of two selected uropathogenic strains of E. coli. This work also showed that a preliminary exposure of bacteria to PAC A2 significantly reduced the adhesion. This phenomenon has been also observed with a lesser impact when uroepithelial cells were pretreated with PAC A2. Moreover, the assays were more robust when bacteria were in fast growing conditions (exponential phase): the adhesion to uroepithelial cells was greater. Significant reduction of adhesion to urepithelial cells was observed: around 80% of inhibition of adhesion with the cranberry extracts at equivalent PAC concentration of 50 μg/mL. The effects of the different assayed extracts were not obviously different except for extract B, which inhibited approximately 55% of adhesion at an equivalent PAC concentration of 5 μg/mL.