Semen Microbiome Could Play a Role in Male Fertility, Other Seminal Health Issues

Gut microbiome and vaginal microbiome aren't new, but a recent study found out that there's semen microbiome too. Also, researchers found a link between it and the male's fertility.

Semen Microbiome Is a Thing

In a new study, a team of researchers at the University of California has discovered a connection between the sperm's health and motility and the bacteria that make up the semen microbiome, affecting the sperm's ability to procreate.

Bacteria usually do not travel with sperm and its seminal fluid supply, which protects them from the testes for most of their journey. This alters as it moves through areas of the penis that are filled with microbes, essentially acquiring its supply of flora.

Semen samples from 73 cisgender men who were at least 18 years old were examined by the researchers. These men were either seeking a fertility evaluation or, if they had already fathered children, seeking advice on a vasectomy.

Compared to the 46 men whose sperm motility was normal, the semen from the 27 men with impaired sperm motility contained a higher quantity of one specific bacteria, Lactobacillus iners.

L. iners are not limited to sperm reproductive fluid. Though too much of it might lower fertility rates and pave the way for bacterial vaginosis, STDs, and pregnancy difficulties, it is typical and even essential at specific levels in the vaginal microbiota.

Semen Microbiome and Fertility

According to the study, L. iners may directly affect male fertility. It creates inflammatory L-lactic acid preferentially, and in certain species, this has been shown to decrease sperm motility. Though it's not yet led to be the reason, that might explain why the sperm in semen samples contaminated with L. iners were having difficulties or struggling.

The men's semen included three types of Pseudomonas bacteria, which were present independent of the normal or aberrant sperm concentration. In contrast to the 53 samples with normal sperm counts, P. putida was less common, and P. fluorescens and P. stautzeri were more abundant in the 20 samples with aberrant sperm concentration.

This discovery implies that the link between reproductive measurements and microorganisms, even closely related ones, may not always be the same.

It's too soon to tell how, if at all, the diversity of bacteria and the makeup of the semen microbiome affect sperm and fertility. It is possible, for example, that some completely separate factor influencing sperm statistics and bacterial levels is the cause of the association between them.

The semen microbiome appears to have a wealth of potential for fertility therapies and other seminal health issues, even if current research only scratches the surface.

"There is much more to explore regarding the microbiome and its connection to male infertility," said the study's lead author, urologist Vadim Osadchiy from the University of California.

"Our research aligns with evidence from smaller studies and will pave the way for future, more comprehensive investigations to unravel the complex relationship between the semen microbiome and fertility."

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