Experts have identified a particular type of vaginal bacteria linked to recurrent urinary tract infections (UTIs).

Millions of women around the world experience recurrent bladder infections. Many recurrent UTIs are thought to occur when dormant E. coli present in the lining of the bladder are reactivated, causing a new infection. However, potential triggers of this reactivation have remained unclear.

International researchers have been looking into the idea that  the idea that certain vaginal bacteria, which are mechanically transferred to the urinary tract during sexual activity, may damage bladder tissue and lead to reactivation of E. coli infection.

In a recent study in mice, exposure of the bladder to the common vaginal bacterium Gardnerella vaginalis awakened dormant Escherichia coli and triggered recurrent UTIs.

Mice exposed to G. vaginalis, which was eliminated rapidly from the bladder, were also more likely to experience life-threatening consequences of the recurrent E. coli UTI, including severe kidney damage and systemic infection. 

The effects of G. vaginalis persisted after the bacterium was no longer present in the urinary tract.

These results could be the first plausible trigger of recurrent UTIs from dormant E. coli in the bladder.

They could also help explain previously found links between vaginal bacteria species, sexual activity, and risk of recurrent UTIs in women.

Recurrent UTIs are usually treated with antibiotics to kill the E. coli. If occasional exposure to G. vaginalis does, indeed, cause recurrent infection in some women, then it could serve as a potential new target of treatments to prevent recurrent UTIs. In light of the rise of multi-drug resistant E. coli, such a strategy could prove especially appealing.

“One of the important findings of this study is that Gardnerella can cause damage to organs of the urinary tract even in the absence of E. coli.,” explains Dr Amanda Lewis of Washington University School of Medicine.

 “This has exciting implications, suggesting that Gardnerella exposures to the bladder could be important for urologic diseases beyond recurrent UTI that we don’t fully understand.”

The study is accessible here.