According to Gram Research analysis, men with low sperm motility have significantly different bacteria living in their urine compared to fertile men, with 18 specific bacterial types showing different abundance levels between the groups. A 2026 case-control study found that bacteria like Porphyromonas, Corynebacterium, and Finegoldia were more common in men with fertility problems, while Blautia and Bacteroides were more abundant in fertile men. These urinary bacterial differences suggest that bacteria beyond the semen and gut may influence male fertility, though more research is needed to prove whether changing these bacteria could improve sperm health.
Researchers discovered that men with low sperm motility, a common cause of male infertility, have different bacteria living in their urine compared to fertile men. Using genetic testing, scientists found 18 types of bacteria that differ between the two groups, with certain bacteria more common in men struggling with fertility. The study suggests that bacteria in the urinary tract, not just in semen or gut, may play a role in sperm health. While these findings are promising for understanding male infertility, more research is needed to prove whether changing these bacteria could improve fertility.
Key Statistics
A 2026 case-control study published in Basic and Clinical Andrology found that men with asthenozoospermia (low sperm motility) had significantly different urinary bacterial communities compared to fertile controls, with 18 bacterial genera showing meaningful differences in relative abundance.
According to the 2026 research, three bacteria (Porphyromonas, Corynebacterium, and Finegoldia) were significantly more abundant in men with low sperm motility, while Blautia and Bacteroides were more common in fertile men.
The study identified differences in multiple metabolic pathways between the two groups, including DNA replication and repair, cell wall building, and B vitamin metabolism, suggesting altered functional capabilities of urinary bacteria in men with fertility problems.
The Quick Take
- What they studied: Whether the bacteria living in the urine of men with low sperm motility differ from the bacteria in fertile men’s urine
- Who participated: Men diagnosed with asthenozoospermia (low sperm motility) and age-matched fertile men without fertility problems
- Key finding: Men with low sperm motility had significantly different bacterial communities in their urine, with 18 specific bacterial types showing different amounts between the two groups
- What it means for you: This research opens a new area for understanding male infertility. If you’re struggling with fertility, your doctor might eventually test urinary bacteria as part of diagnosis, though this is not yet standard practice. The findings suggest that treating urinary bacteria imbalances could become a fertility treatment option in the future.
The Research Details
This was a case-control study, which means researchers compared two groups of men: those with asthenozoospermia (low sperm motility) and healthy fertile men of similar age. Urine samples were collected from all participants and analyzed using genetic sequencing, a technique that identifies which bacteria are present and in what amounts. The researchers used a method called 16S rRNA gene sequencing, which is like taking a genetic fingerprint of all the bacteria in a sample. They then compared the bacterial communities between the two groups to see what differences existed.
The study examined two types of bacterial diversity. Alpha diversity measures how many different types of bacteria are present in one person’s urine. Beta diversity measures how different the bacterial communities are between different people. The researchers also predicted what functions these bacteria might perform based on their genetic makeup, looking at processes like energy production and nutrient metabolism.
Previous research focused almost entirely on bacteria in semen and the gut, overlooking the urinary tract as a potential factor in male infertility. This study is important because it expands our understanding of where bacteria might influence sperm health. By identifying specific bacterial differences in men with fertility problems, scientists can develop new diagnostic tools and potential treatments. Understanding the urinary microbiota could lead to new ways to help men with infertility.
This study used rigorous genetic sequencing methods to identify bacteria, which is more accurate than older techniques. The researchers compared men with the same condition to controls matched by age, which helps ensure fair comparisons. However, the study does not prove that these bacterial differences cause infertility, only that they are associated with it. The sample size was not clearly reported, which limits how confident we can be about the findings. The study is observational, meaning it shows correlation but not causation.
What the Results Show
The most striking finding was that men with low sperm motility had a different overall bacterial community structure in their urine compared to fertile men. While the total number of different bacterial types was similar between groups, the specific bacteria present and their relative amounts differed significantly. Eighteen bacterial genera (groups of related bacteria) showed meaningful differences in abundance between the two groups.
Three bacteria were more common in men with low sperm motility: Porphyromonas, Corynebacterium, and Finegoldia. In contrast, two bacteria were more abundant in fertile men: Blautia and Bacteroides. These differences were statistically significant, meaning they were unlikely to occur by chance. The researchers also predicted what metabolic functions these different bacterial communities might perform. They found differences in multiple pathways related to energy production, nutrient processing, and genetic information handling.
The predicted functional analysis revealed that the bacterial communities in men with low sperm motility had altered capabilities in several important metabolic processes. These included differences in DNA replication and repair, cell wall building (peptidoglycan biosynthesis), folate metabolism (important for cell division), and nicotinate and nicotinamide metabolism (B vitamins important for energy). These functional differences suggest that the urinary bacteria in men with fertility problems may not be supporting sperm health as effectively as bacteria in fertile men.
This research extends previous findings about the microbiome and male infertility. Earlier studies focused on bacteria in semen and the digestive tract, showing that these bacteria influence sperm quality. This study is novel because it examines the urinary microbiota, a compartment that had been largely ignored in fertility research. The findings suggest that the entire urinary and reproductive system’s bacterial communities may work together to influence male fertility, not just the semen or gut alone.
The study does not establish cause and effect. It shows that men with low sperm motility have different urinary bacteria, but it does not prove that these bacteria cause the fertility problem or that changing them would improve fertility. The sample size was not clearly reported, making it difficult to assess how reliable the findings are. The study is cross-sectional, meaning it captured a single moment in time rather than following men over months or years. Without longitudinal data, we cannot know whether bacterial changes precede fertility problems or result from them. The study also did not measure whether these bacterial differences actually affect sperm function through specific biological mechanisms.
The Bottom Line
This research is preliminary and does not yet support clinical recommendations for treating urinary bacteria to improve fertility. Men with fertility concerns should continue working with fertility specialists using established diagnostic and treatment approaches. Future research may lead to urinary microbiota testing as part of male fertility evaluation, but this is not yet standard practice. Confidence level: Low to Moderate. This is early-stage research that requires confirmation through larger studies and mechanistic investigations.
Men experiencing infertility or low sperm motility should be aware of this emerging research area, though it should not change current treatment decisions. Fertility specialists and urologists may find this research interesting for understanding male infertility mechanisms. Researchers studying the microbiome and reproductive health should consider this work as it opens new research directions. Men without fertility concerns do not need to act on these findings.
If urinary microbiota testing becomes a clinical tool, it would likely take 5 to 10 years of additional research before it becomes standard practice. Any potential treatments targeting urinary bacteria would require similar development and testing timelines. Men seeking fertility treatment should not delay seeking established care while waiting for these emerging approaches.
Frequently Asked Questions
Can bacteria in urine cause low sperm motility?
This study shows that men with low sperm motility have different urinary bacteria, but it does not prove bacteria cause the problem. The association is clear, but researchers need more studies to establish whether changing these bacteria would improve fertility.
Should I get my urinary bacteria tested if I have fertility problems?
Urinary microbiota testing is not yet standard for male fertility evaluation. Continue working with your fertility specialist using established diagnostic methods. This research may lead to new testing options in the future, but that development typically takes several years.
Can probiotics help improve sperm motility by changing urinary bacteria?
There is no evidence yet that probiotics targeting urinary bacteria improve sperm motility. While this research identifies bacterial differences, it does not demonstrate that specific probiotic treatments would help. Consult your doctor before starting any supplements for fertility.
What bacteria should I avoid or encourage in my urinary tract?
This research is too preliminary to make specific recommendations about which bacteria to encourage or avoid. The study identifies associations but does not establish that promoting or eliminating specific bacteria would improve fertility. More research is needed before clinical recommendations can be made.
How does urinary bacteria relate to gut bacteria and semen bacteria in male fertility?
This study suggests that bacteria in the urinary tract, gut, and semen may all influence male fertility as interconnected systems. Previous research focused on gut and semen bacteria, but this work shows the urinary microbiota also matters. How these three bacterial communities work together remains unclear.
Want to Apply This Research?
- Track urinary health markers including frequency of urinary tract infections, symptoms like burning or urgency, and any antibiotic treatments. Note dates and types of antibiotics used, as these affect bacterial communities. Record this monthly alongside any fertility treatment progress.
- Users can log lifestyle factors that support urinary and reproductive health: daily water intake (target 8-10 glasses), urinary tract health practices, and any probiotic or prebiotic foods consumed. Track correlations between these behaviors and any fertility-related metrics being monitored with a healthcare provider.
- Establish a baseline of urinary health habits and symptoms. Monitor for changes in urinary tract health over 3 to 6 months while working with a fertility specialist. If urinary microbiota testing becomes available through your doctor, use the app to track results over time and correlate with lifestyle changes and fertility outcomes.
This research is preliminary and does not establish that urinary bacteria cause low sperm motility or that treating urinary bacteria will improve fertility. Men with fertility concerns should consult with a qualified fertility specialist or urologist for diagnosis and treatment. This article is for educational purposes and should not replace professional medical advice. Do not start, stop, or change any fertility treatments based on this research without consulting your healthcare provider. Urinary microbiota testing is not yet a standard clinical tool for male fertility evaluation.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.