The effect of local estrogen therapy on the urinary microbiome composition of postmenopausal women with and without recurrent urinary tract infections

Introduction and hypothesis: Recurrent urinary tract infections (rUTIs) occur in 2–10% of postmenopausal women. Local estrogen therapy (LET) has been shown to reduce UTIs. This study aimed to compare the urinary microbiome between patients with and without a history of rUTIs and to examine whether treatment with LET influences the diversity and richness of microbiome species in two groups. Methods: Postmenopausal women with and without rUTIs attending the urogynecology clinic between April 2019 and December 2020 were recruited. Participant baseline characteristics and demographics were recorded. Aseptic transurethral urine samples were collected at recruitment and at 3–6 months following treatment with LET. The V1–V2 and ITS regions of the 16S rRNA gene were sequenced to identify bacteria. Results: A total of 37 women were recruited, 20 controls and 17 patients with rUTI. During follow-up, symptomatic UTIs occurred in 3/17 (17.6%) and 0/20 in the rUTI group and control group, respectively. Klebsiella aerogenes was present in 80% of rUTI samples and in 53.3% of control samples before LET. Abundance of Finegoldia magna was present in 33.3% of samples before LET, but only in 6.7% after LET. There was no change in relative abundance of lactobacillus species following LET in both groups. Conclusions: Treatment with vaginal LET altered the local hormonal environment of the urinary bladder and likely protected women from development of rUTI by decreasing the presence of F. magna. To confirm the significance of this bacterial species in rUTI symptomatology, our finding needs to be validated on a larger patient cohort.