A recently identified bacteria in semen could harm sperm motility and cause fertility problems, reveals a study by American researchers.
Around half of infertility situations within a couple are attributable to the man, recall the authors of the study.
“The problem is that we don’t really know what the causes of the problem are in humans,” commented Professor Bernard Robaire, who teaches in the department of obstetrics and gynecology at McGill University. Half to two thirds of cases are idiopathic and it is not really clear what the source is. »
It is only recently that scientists have discovered that sperm is not a sterile environment and that it has its own microbiome, but no exhaustive inventory of this microbial flora has ever been carried out before.
Researchers at the University of California at Los Angeles took on the task by studying the sperm of 73 men; half of them were already fathers, and the other half had consulted for fertility problems.
The study authors identified five bacteria common to both groups, but high levels of the bacteria Lactobacillus iners were associated with motility problems (the ability of sperm to “swim” effectively) in the infertile group.
The researchers point out that this same bacteria is also found in the vaginal microbiome, and that high levels can also be associated with fertility problems in women.
This study is only the very first to address the issue, and researchers are therefore far from understanding how the L. iners bacteria interferes with sperm motility. One hypothesis involves inflammation caused by the bacteria.
Other studies, however, have found an association between other members of the Lactobacillus family and motility problems – which could mean that the bacteria actually plays a useful role in curbing less vigorous sperm to allow those who are are the healthiest to join the egg.
“The question we need to ask is: ‘Are these bacteria present in the reproductive system or are they associated with other tissues?’” asked Professor Robaire. It is not yet clear where and how these bacteria are introduced into the reproductive system. »
That being said, he continues, the identification of this bacteria in the semen of men who have fertility problems could eventually lead to new diagnostic tests, or even treatments, even if this is not for tomorrow.
Unfortunately, the effectiveness of fertilization in vitro has reduced the amount of research being done on the causes of male infertility, recalled Professor Robaire. And even if the problem is on the man’s side, it will often be the woman who suffers the consequences of the treatment, “so it is very important to try to understand the source of infertility in men.”
“In vitro fertilization is an easy solution,” said Professor Robaire. But it is a solution that is expensive for patients and fertilization clinics benefit from it from a financial point of view. »
The findings of this study were published by the journal Scientific Reports.