Inhibitory activity of Cranberry extract on the bacterial adhesion in human urine: an ex vivo study

The initial step of urinary tract infections (UTIs), frequently caused by uropathogenic Escherichia coli (UPEC), is the adhesion of bacteria to urothelial cells.

Extracts from Cranberry fruits (Vaccinium macrocarpon Ait.) have long been associated with the prevention of UTIs.

Within ex vivo experiments in a pilot study, a significant inhibition of bacterial adhesion of UPEC NU14 to human T24 bladder cells was achieved using urine from 4 volunteers after consumption of standardized Cranberry extract (CE). The antiadhesive effect of the extract was directed only against the bacterial adhesin FimH, not against P-fimbriae dominated UPEC [1].

To verify these data, a further in vivo study included 18 volunteers, 900 mg CE daily over 8 days. The obtained urine exerted a time-dependent, significant inhibition of the adhesion of UPEC UTI89 to human T24 bladder cells ex vivo, but did not affect the adhesion of E. coli 2980.

To investigate the effect of the Cranberry metabolites on UPEC transcriptome analysis of UTI89 by Next Generation Sequencing was performed. The transcriptome of bacteria grown in urine collected after 7 days of cranberry intake indicated no relevant differences compared to that obtained from bacteria grown in control urine.

Therefore, the antiadhesive activity of urine after CE intake can be explained by an effect on bacterial adhesin assembly or a direct interaction of cranberry metabolites with bacterial adhesins, probably of the FimH class.

LC-MS/MS study of the urine was performed to correlate Cranberry-related metabolites with the antiadhesive effects.

[1] Rafsanjany N, Sendker J, Brandt S, Dobrindt U, Hensel A. J Agricult Food Chem 2015; 63: 8804 – 8818.