Vaginal sex impacts male urethral and penile microbiome.

A new study shows that the urethra of healthy men is teeming with microbial life and that vaginal sex can shape its composition. The research provides a healthy baseline for clinicians and scientists to contrast between healthy and diseased states of the urethra, an entrance to the urinary and reproductive systems. The study found that most of the healthy men had a simple, sparse community of oxygen-loving bacteria in the urethra, but some of the men also had a more complex secondary group of bacteria that are often found in the vagina and can disturb the healthy bacterial ecosystem of the vagina. The team speculates that these bacteria reside deeper in the penile urethra because they thrive in oxygen-scarce settings. Only men who reported having vaginal sex carry these bacteria, hinting at the microbes' origins.