The penis plays host to a collection of bacteria known as the penile microbiome, and an analysis of urethral swabs has found that men who have vaginal sex can pick up bacteria normally found in the vagina
By Soumya Sagar
21 March 2023
A transmission electron micrograph of a colony of Gardnerella vaginalis, bacteria that are found in vaginas and the urethras of men who have vaginal sex
MOREDUN ANIMAL HEALTH LTD/SCIENCE PHOTO LIBRARY
The male urethra – the tube through which urine exits the body – is home to an array of bacteria, some of which are probably picked up during vaginal sex.
Evelyn Toh at the Indiana University School of Medicine and her colleagues swabbed the urethras of 110 men who had no sexually transmitted infections or urethra-related issues. The men, average age 28, came from a range of ethnic and racial backgrounds. Transgender people weren’t included in the study.
Of these men, 92 provided swabs with sufficient levels of bacterial DNA for further analysis.
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The detected bacteria could be separated into two groups – those that can live in the presence of oxygen and therefore probably dwell near the tip of the penis, and those that cannot live when oxygen is present and therefore probably dwell higher up in the urethra.
The former group was found in most of the men’s swabs and are probably native to the penile urethra, according to the researchers.
The latter group, however, was dominated by bacteria that are often disrupted in the condition bacterial vaginosis (BV), a common cause of unusual vaginal discharge that is thought to come about when the vagina’s microbiome gets out of sync.