Marked sex differences and frequent carriage of recognized uropathogens in the human urogenital microbiome: urine profiles from a population-level shotgun metagenomics study

Background: The urinary tract was long considered sterile. The discovery of the urinary microbiome has attracted interest in its role in urinary health and disease. Population-level urinary microbiome composition remains poorly defined and previous studies relied on selected populations and low-resolution sequencing. We characterized the microbial composition of voided urine from adults without urinary symptoms in a large Swedish population cohort to establish a population-based reference for microorganisms detected in voided urine using shotgun metagenomics. Methods: We performed shotgun metagenomic sequencing of voided urine samples from 2,062 participants of the population-based Swedish CArdioPulmonary bioImage Study (SCAPIS; 55% women, 50-65 years). Results: Among 3,668 identified species, 90% were classified at the species level. Microbial profiles differed substantially between sexes, with lactobacilli and bifidobacteria enriched in females, while Cutibacterium acnes, Enterococcus and Propionimicrobium lymphophilum were enriched in males. Recognized uropathogens, including Enterococcus faecalis and Escherichia coli, were frequently detected despite participants having no urinary symptoms. Males showed higher alpha diversity (Shannon and inverse Simpson indices), whereas richness did not differ by sex. Age showed only modest associations with alpha diversity, and beta diversity differed by sex but showed minimal age-related variation. Conclusions: This study provides a population-based reference for interpreting microorganisms detected in routine voided urine samples. Biological sex was the principal determinant of microbial composition, supporting routine consideration of sex in future studies of the urogenital microbiota using routine voided urine samples.