Altered microbial colonization of the urogenital tract in female overactive bladder syndrome

The discovery of a resident urinary microbiome has challenged the long-standing view of the bladder as sterile. Overactive bladder, a common and burdensome condition, has been linked to urinary dysbiosis, yet the origins of bladder colonization and its relationship to adjacent microbiomes remain unclear.

To compare the urinary microbiome profiles of women with overactive bladder to those of healthy controls, to assess intraindividual relationships between the urinary and other urogenital or mucosal microbiomes-including the vaginal, urethral, buccal sites, and stool-and to identify potential colonization pathways by analyzing microbial overlap within and between individuals.

In a cross-sectional study, we profiled the microbiomes of 50 women with overactive bladder and 49 healthy controls across urine, urethra, vagina, oral cavity, and stool. DNA was extracted using standardized protocols and the V3 to V4 region of the 16S rRNA gene was sequenced on the Illumina MiSeq platform. Reads were processed with Divisive Amplicon Denoising Algorithm 2 and taxonomically classified using the SILVA ribosomal RNA database. Diversity metrics (alpha and beta diversity), differential abundance testing (DESeq2), and cross-site microbial overlap analyses were performed in R using established packages (phyloseq, vegan, mia, and microViz). Subgroup analyses accounted for menopausal status.

Overactive bladder cases exhibited higher alpha diversity in urethral and vaginal samples and significantly different beta diversity across all sites compared with controls (P<.004). The urethra of overactive bladder cases contained reduced Lactobacillus but was enriched with Bacteroides, Bifidobacterium, Gardnerella, Hydrotalea, Streptococcus, and other genera. Six taxa (Alistipes, Bacteroides, Bifidobacterium, Bradyrhizobium, Hydrotalea, and Neisseria) consistently met thresholds for abundance and prevalence in urethra and were also elevated in overactive bladder urine, vagina, and oral cavity, but not stool. Intraindividual analyses showed greater urethra-urine and urethra-vagina divergence in overactive bladder than in controls, indicating disruption of the normal microbial continuum. Subgroup analyses confirmed between-group differences irrespective of menopausal status. Notably, dysbiosis in overactive bladder over-rode the premenopausal/postmenopausal contrasts observed in controls.

Women with overactive bladder seem to have a distinct multisite dysbiosis, most pronounced in the urogenital tract, characterized by the loss of Lactobacillus and enrichment of selected taxa across urethra, urine, vagina, and oral cavity. The observed microbial overlap across urogenital sites, compared with stool, is consistent with predominant urogenital microbial relatedness in this cross-sectional cohort. These findings provide insight into microbiome alterations in overactive bladder and highlight the need for longitudinal studies to clarify mechanisms and evaluate potential microbiome-targeted strategies. Given the cross-sectional design, these findings describe associations and cannot establish causality or the directionality of microbial transmission between compartments.