A recent clinical trial provides new data on the microbiota of the penis. It reveals that bacteria in the male urethra come from two distinct sources, one of which is specific to men who have vaginal sex.
The urethra is not spared, and like many organs, it is colonised by micro-organisms. However, it is possible to distinguish not one, but two microbiota within the penis. In a study published on 21 March 2023 in Cell Reports Medicine on 110 men, the results reveal the presence of bacteria in the male urethra from two different sources.
These two microbiotas, named in the study UT1 and UT2 for Uretrotypes 1 and 2, differ in terms of composition.
Microbiota of the penis UT1: the core microbiome
According to the researchers, the human urethra generally harbours a characteristic baseline microbiome.
This is located at the tip of the penis and consists mainly of aerobic bacteria, i.e. bacteria that can grow in the presence of oxygen.
Thus, most of the samples collected show a simple, homogeneous, and not very diversified bacterial composition. Indeed, the UT1 microbiota is mainly composed of Corynebacterium and Streptococcus, with a marked abundance of S. mitis.
Microbiota of the penis UT2: the sex-dependent microbiome
According to the study, this microbiome is dependent on a man’s sexual activity. The effects of different types of sex (vaginal, oral, and rectal) were studied.
Thus, men who had vaginal sex developed a second bacterial community, located slightly deeper in the urethra.
Compared to the microbiota analysed in UT1, the bacterial community would be more:
- Rich,
- Complex,
- Diversified,
- Anaerobic.
The species observed in this urethrotype are also those commonly found in women with bacterial vaginosis such as Gardnerella vaginalis, suggesting that they colonise healthy men from their female partners.
Thus, the bacteria associated with vaginal dysbiosis are only detected in men who have vaginal sex.
Bacterial vaginosis, a possible male STI*?
Although not currently considered as such, researchers are making this assumption based on the results obtained. Indeed, it is possible to detect the influence of the vaginal microbiota on the penile microbiota up to 60 days after intercourse. According to them, this could explain the transmission of these bacteria to the different partners and thus cause bacterial vaginosis.
Nevertheless, further studies are needed to validate or invalidate these results.
LC
References
* Sexually Transmitted Infection
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