Semen, a reflection of a man’s intimate microbiota

A new method of semen analysis has the potential to replace traditional techniques. Used to detect microorganisms that colonize or infect the male genital tract, the traditional methods are considered too expensive for some laboratories or of limited use.

 

Although it is by far the most well-known microbiota, as it is the most important and most studied, the gut microbiota is not the only microbial community in our body. Bacteria, viruses and yeasts colonize all our bodily fluids, even the most intimate. A team of American researchers has set out to identify and analyze the microorganisms present in semen using a technique normally used to assess whether genes are functional. Their aim was to determine whether this approach is suitable for evaluating the diversity of the microbiota in semen.

Less rich but more diverse than vaginal microbiota

The microorganisms residing in the male genital tract come mainly from direct contact with women during sexual intercourse. Escherichia coli, which is linked to genital and urethral infections, is the most frequently observed bacterium. The male genital microbiota shares 85% of its bacterial species with the vaginal microbiota but is less abundant and more diverse.

An infected sample

The researchers analyzed the semen of 85 men who were in a heterosexual relationship. The technique used by the researchers made it possible to identify the main bacteria colonizing the male genital tract. Only one sample had a very different microbial mix, showing a particularly high content in Streptococcus agalactiae. This bacterial species is responsible for sexual infections in both men and women and may lead to miscarriage or stillbirth in the latter. Its abundance is difficult to explain, with the most likely cause being infection via the subject’s partner.

An effective diagnostic technique

The authors conclude that this new method appears just as effective in diagnosing bacterial colonization or infection of semen as the method traditionally used to analyze human microbiota.

 

Sources: 

Swanson GM, Moskovtsev S, Librach C, et al. What human sperm RNA-Seq tells us about the microbiome. J Assist Reprod Genet. 2020;37(2):359–368. doi:10.1007/s10815-019-01672-x