- Design
- Pilot multicentre, double-blind, placebo-controlled randomised 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), p=0.089
An Italian multicentre pilot trial randomised 50 women with recurrent uncomplicated urinary tract infections to the probiotic Escherichia coli Nissle 1917 or placebo, double-blind, with 26 weeks of follow-up. Recruitment was cut short by the COVID-19 pandemic.
At least one microbiologically confirmed recurrence occurred in 16.7% on the probiotic and 42.3% on placebo (RR 0.39, 95% CI 0.14–1.14), a difference that did not reach statistical significance. Positive cultures at 12 weeks were also less frequent, and the vitality domain of quality of life improved more. Side effects were mild and mainly gastrointestinal.
This is a small pilot with a non-significant primary result. It justifies a proper trial, not routine use. It was published on 28 September 2026.
- Treat E. coli Nissle 1917 for recurrent UTI as investigational; the primary result was not significant.
- Use established preventive measures first.
- Watch for an adequately powered trial.
- Gastrointestinal side effects were mild in this pilot.
Why it matters
Non-antibiotic prevention of recurrent UTI is a real need, and this is a candidate worth testing properly.
Don't overread it
With 50 women and a confidence interval crossing 1, chance cannot be ruled out.
The statistics, in plain English
A relative risk of 0.39 suggests about 60% fewer recurrences, but the interval (0.14–1.14) includes 1, meaning no effect is still possible. Small pilot trials often overestimate benefits that shrink in larger studies.
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