Role of Vaginal Microbiota and Oral Lactobacillus Supplementation in Recurrent Urinary Tract Infections of Menopausal Women: Protocol for the VaMirUTI Cohort Study

(1) Background: Recurrent urinary tract infections (rUTIs) are common among peri- and postmenopausal women, partly due to hormonal changes that disrupt the vaginal microbiota. A reduction in <i>Lactobacillus</i> dominance is associated with increased risk of rUTI. Although antibiotics remain the standard of care, their use contributes to the emergence of multidrug-resistant pathogens. Probiotics may offer a non-antibiotic alternative; however, clinical evidence remains limited. (2) Methods: The VaMirUTI study is a prospective, monocentric, non-randomized cohort investigating the combined effect of oral probiotics and vaginal estriol on vaginal and urinary microbiota in peri- and postmenopausal women with recurrent UTIs. The primary endpoints are (i) change in <i>Lactobacillus</i> dominance at 3 months and (ii) UTI recurrence at 12 months. A total of 100 women (70 rUTI, 30 controls) will be followed for up to 12 months. Vaginal swabs and urine samples will be collected at baseline, during UTI episodes, and at study completion. Vaginal microbiota composition will be analyzed by 16S rRNA gene sequencing. (3) Results: This protocol outlines the study design and methodology. The primary outcome is the change in vaginal <i>Lactobacillus</i> dominance following the intervention. Secondary outcomes include UTI recurrence rates and the identification of microbiota signatures associated with rUTI. (4) Conclusions: The VaMirUTI study will clarify the relationship between vaginal microbiota, oral probiotic supplementation, and rUTI in menopausal women, potentially informing future non-antibiotic preventive strategies.