Design: Pilot, multicentre, double-blind, randomised placebo-controlled trial
Population: 50 women with recurrent uncomplicated urinary tract infection
Primary outcome: At least one microbiological recurrence over 26 weeks
Effect: 16.7% vs 42.3%; RR 0.39 (95% CI 0.14-1.14)

This pilot double-blind trial randomised 50 women with recurrent uncomplicated urinary tract infection to the probiotic Escherichia coli Nissle 1917 or placebo for 26 weeks. Recruitment fell short during the COVID-19 pandemic.

At least one culture-confirmed recurrence occurred in 4 of 24 (16.7%) on the probiotic and 11 of 26 (42.3%) on placebo (RR 0.39, 95% CI 0.14 to 1.14). Mild gastrointestinal upset was the main side effect.

The direction is encouraging for a non-antibiotic option, but the result is not statistically significant and the trial was too small to settle the question.

Do not recommend this probiotic for recurrent urinary infection on the basis of this pilot.
Use established measures first: hydration advice, review of spermicide use, vaginal oestrogen after menopause.
Confirm recurrences with culture before long-term prophylaxis.
Discuss non-antibiotic prophylaxis options where evidence supports them, to limit resistance.

Why it matters

A non-antibiotic route to prevention is worth a proper trial in an era of rising resistance.

The statistics, in plain English

A relative risk of 0.39 suggests recurrences might be roughly halved, but the confidence interval runs from 0.14 to 1.14, which includes no effect. With 50 women, a chance result is entirely possible.