Alterations in urinary microbiota composition and function in men with Asthenozoospermia: a case-control study

Asthenozoospermia (AZS) is a leading cause of male-factor infertility, yet the contribution of the urinary microbiota to sperm motility remains poorly defined, because previous work has focused almost exclusively on the seminal and gut microbiota. Here we used 16S rRNA gene sequencing to characterize the composition and functional profiles of the urinary microbiota in men with AZS and in fertile controls.

Isolated AZS and age-matched fertile controls were enrolled, and urinary specimens from participants were sequenced successfully. Alpha diversity of the urinary microbiota did not differ between the two groups. In contrast, beta diversity analysis revealed a statistically significant difference in overall community structure, although the group effect was modest in magnitude (PERMANOVA on Bray-Curtis dissimilarities, R² = 0.13, p = 0.001). Eighteen genera differed significantly in relative abundance. Porphyromonas, Corynebacterium, and Finegoldia were more abundant in men with AZS, whereas Blautia and Bacteroides were more abundant in controls. Predicted functional analysis identified multiple metabolic and genetic-information-processing pathways that differed between the groups, including replication and repair modules, peptidoglycan biosynthesis, one-carbon pool by folate, and nicotinate and nicotinamide metabolism.

It appears that men with AZS exhibit altered urinary microbiota structure and predicted functional profile. These associations extend the microbiome-male-infertility axis beyond the seminal and gut compartments and may inform biomarker discovery and microbiome-modulating strategies, although longitudinal and mechanistic studies are required to establish causality.