Urinary tract infections: cranberries could act directly on the gut microbiota

Salicylate: this component, which is able to restore the composition of the gut microbiota by “depleting” the reservoir of bacteria that are harmful for the urinary tract, might be implicated in the mechanism by which cranberries prevent urinary tract infections.

Created 04 February 2020
Updated 06 October 2021

About this article

Created 04 February 2020
Updated 06 October 2021

Urinary tract infections poison the life of 150 million people worldwide every year and are mainly caused by Escherichia coli. The gut microbiota acts as a reservoir for this uropathogenic bacterium of the Enterobacteriaceae family: when excreted in the stools, it colonizes the periurethral region and infects the urinary tract. Despite inconsistent results regarding their efficacy, it is advised to eat cranberries to prevent relapses. These small red berries seem to deplete this reservoir of enterobacteria that are responsible for urinary infections by acting as a prebiotic or antimicrobial agent on the gut microbiota.

Cranberries: pure or in extracts

To determine which components are at the origin of this effect, an American team analyzed the impact of 44 active ingredients found in cranberries on the bacterial profile of the human gut microbiota. To this end, the researchers used a simulator replicating the human microbiota, that was created using stool samples with an increased or decreased content of enterobacteria. They then daily inoculated either cranberry powder, or extracts spiked with or deprived of polyphenols. According to several in vitro studies, the antimicrobial or anti-adhesive properties of polyphenols could explain the efficacy of cranberries to prevent urinary tract infections.

Salicylate was the most active component

After five days, the researchers observed an increase in the number of beneficial bacteria within the gut microbiota, and a decrease in the number of enterobacteria in all samples. The most notable changes were observed with cranberry powder, which suggests that all components–polyphenols and other molecules– act together to change the microbiota. However, salicylate is the component that proved to be the most important. One question that remains is whether this is due to its antimicrobial or its prebiotic effect on the enterobacteria responsible for urinary tract infections.

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O’Connor K, Morrissette M, Strandwitz P et al. Cranberry extracts promote growth of Bacteroidaceae and decrease abundance of Enterobacteriaceae in a human gut simulator model. PLoS ONE 14(11). 2019; https://doi.org/10.1371/journal.pone.0224836

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