Key points are not available for this paper at this time.
Abstract Study question Does seminal microbiome differ between men with good and poor sperm quality parameters? Summary answer Men with poor sperm quality values presented a higher microbial richness, while after rigorous contamination controlling no specific bacteria associated with sperm quality parameters. What is known already Infertility represents a major health concern affecting 1 in every 6 couples. Approximately 50% of infertility cases are attributed to male factor, where seminal quality is crucial. Recent studies have brought to light the role of the microbiome in sperm quality and function. Changes in microbial communities can impact reproductive functions, as these microorganisms may affect spermatozoa by releasing specific molecules or influencing direct adhesion. Since current evidence in the field is inconclusive, as the studies are performed on small sample sizes and lack proper positive and negative controls, there is a need for rigorous studies on bigger cohorts. Study design, size, duration This cross-sectional study included 115 men (age= 33.6±9.6 years; BMI= 25.0±3.5). Semen samples assessment was performed between March 2019 and July 2021 at the sperm biobank and University Hospital. The study was approved by the regional Ethics Committee. Participants/materials, setting, methods The study population was categorized into two seminal quality groups based on WHO reference values. Accordingly, 66 men presented good sperm quality while 49 poor sperm quality. Sperm concentration and progressive motility parameters were assessed in semen. Seminal microbiome was analyzed using 16 rRNA gene sequencing. For rigorous contamination controlling, negative controls together with in silico decontamination (MicroDecon package) were applied. Microbial diversity and composition were assessed including age and BMI as confounders. Main results and the role of chance After rigorous decontamination analysis including negative controls, 774 microorganisms were identified in the semen. Ninety-one bacteria were detected as contaminants. Next, a filter of 30% prevalence was applied to identify the core seminal microbiome, which resulted in a total of 36 bacterial genera in the semen in our cohort of men. Bacteria such as Actinomyces, Finegoldia, Campylobacter, Anaerococcus and Peptoniphilus were the the most prevalent among seminal samples. Men with poor sperm quality presented a richer seminal microbiome compared to good sperm quality group (α-diversity p-value=0.022), while β-diversity did not show a significant microbial dissimilarity between groups (R2=0.012, p-value0.05). Differential abundance analysis on the core microbiome detected increased abundances of Veillonella (logFC=1.836), Gemella (logFC=1.612) and a member of Pasteurellaceae family (logFC=1.628) in men with lower sperm quality (all p-values0.05). However, differences did not remain significant after multiple comparison correction (FDR p-values0.05). Limitations, reasons for caution This study reported specific microbial alterations in men with poor sperm quality parameters, which should be investigated further considering different life-style factors such as smoking and diet. Wider implications of the findings With our rigorous study protocol, we see that although seminal microbiome could have some potential implications on seminal quality, the core microbiome does not seem to associate with seminal parameters. More research is needed, but it could be there has been previously overinterpretation of the microbiome associations with seminal parameters. Trial registration number not applicable
Folch et al. (Mon,) studied this question.