Recurrent UTIs linked to gut microbiome, chronic inflammatio
A new study suggests that women who get recurrent UTIs may be caught in a vicious cycle in which antibiotics given to eradicate one infection predispose them to develop another. A round of antibiotics eliminates disease-causing bacteria from the bladder but not from the intestines. Surviving bacteria in the gut can multiply and spread to the bladder again, causing another UTI.

The researchers studied 15 women with histories of recurrent UTIs and 16 women without. All participants provided urine and blood samples at the start of the study and monthly stool samples. The team analyzed the bacterial composition in the stool samples, tested the urine for the presence of bacteria, and measured gene expression in blood samples.

Over the course of a year, 24 UTIs occurred, all in participants with histories of repeated UTIs. When participants were diagnosed with a UTI, the team took additional urine, blood and stool samples. The real difference was in the makeup of their gut microbiomes. Patients with repeat infections showed decreased diversity of healthy gut microbial species, which could provide more opportunities for disease-causing species to gain a foothold and multiply. Notably, the microbiomes of women with recurrent UTIs were particularly scarce in bacteria that produce butyrate, a short-chain fatty acid with anti-inflammatory effects.