The influence of vasectomy on seminal microbiome

Abstract Study question Does male sterilisation with vasectomy induce changes in the seminal microbiome composition? Summary answer Human semen harbours an enriched microbial community and the seminal microbiome composition significantly differed in semen samples from the same men before and after vasectomy. What is known already The semen harbours a polymicrobial community, where Lactobacillus, Corynebacterium, Staphylococcus, Prevotella, and Finegoldia are common. The origin of the seminal microbiome, however, has not yet been established. One-third of the seminal microbes originate from the urethra, whereas a considerable part could originate from the upper genital tract. Similarly, male reproductive organs, such as prostate, seminal vesicles, and testicles contain its own microbiome. Recent pioneering studies analysing a total of 18 men indicates that vasectomy procedure alters the seminal microbiome, suggesting a testicular or epididymal microbial origin. Study design, size, duration This cohort study included 36 men (age = 40.4 ± 5.2 years, BMI = 26.2 ± 3.9 kg/m²) who were planning to undergo vasectomy at the University Hospital from February to June 2021 and volunteered to donate semen samples before vasectomy and 3 months after the procedure. The study was approved by the Ethics Committee of Investigación Biomédica de Andalucia. Participants/materials, setting, methods Samples were collected after washing the penis with soap and water, and after urinating. Semen was obtained by masturbation (3-5 days of abstinence) before the vasectomy and 3 months post-vasectomy. The seminal microbiome was analysed by sequencing the V4 hypervariable region of the 16S rRNA gene (Illumina MiSeq). Raw sequences were pre-processed and taxonomy assigned using Quantitative Insights Into Microbial Ecology version 2 (QIIME2). Bacterial diversity and abundance analyses were performed in R software. Main results and the role of chance Fifty-six bacterial genera were detected in the semen samples, where Campylobacter, Finegoldia, Ezakiella, Streptococcus, Staphylococcus, Corynebacterium, Peptoniphilus, and Anaerococcus prevailed (each genus with a relative abundance ≥5%). Post-vasectomy semen samples had significantly higher alpha diversity (observed richness diversity Wilcoxon signed-rank p-value = 0.035) and markedly increased abundance of genera Porphyromonas, Finegoldia, and Anaerococcus, while Acetobacter genus was reduced when compared with semen samples collected before the vasectomy procedure (FDR p-value<0.05). Beta diversity analysis indicated a significant microbial dissimilarity between seminal samples collected before and after vasectomy (weighted and unweighted PERMANOVA p-value = 0.001). Limitations, reasons for caution This study did not include urine samples, which do share around 30% of the microorganisms with semen. Therefore, in the next step we aim to integrate urine samples into the analysis. Wider implications of the findings Male sterilisation with vasectomy gave rise to fluctuations in the seminal microbiome composition and abundance. Our study findings provide new insight into the origin of seminal microbes, indicating that some accompanying bacteria could originate already from the testicular environment and their changes could entail microbial unbalance in semen. Trial registration number NA