Sexually Transmitted Infections and Male Fertility

Sexually transmitted infections (STIs) represent a significant and often under-recognised cause of male subfertility and infertility worldwide. Bacterial agents such as Chlamydia trachomatis, Ureaplasma spp. and Mycoplasma spp., as well as viral pathogens including human papillomavirus and herpes simplex virus, may colonise the male genital tract without overt symptoms. Infection can provoke local inflammation, disruption of the blood-testis barrier and alterations in semen parameters—most notably reductions in sperm concentration, motility, morphology and increases in DNA fragmentation. Immune-mediated production of reactive oxygen species and prolonged oxido-inflammatory states compound tissue remodelling in the epididymis and seminiferous tubules, impairing spermatogenesis and endocrine function. Global prevalence of STIs in men of reproductive age, coupled with evolving diagnostic and molecular screening tools, has sharpened focus on early detection, pathogen-specific treatment and the potential for antioxidant and anti-inflammatory adjuncts to preserve fertility potential.

Research from Nature Portfolio

Large cohort analysis of primary infertility patients in Argentina revealed significantly higher prevalence of C. trachomatis, Ureaplasma spp. and M. hominis infections in male partners compared to controls, with younger men showing the greatest risk. Reciprocal associations between Ureaplasma and Mycoplasma co-infections highlighted the need for multiplex screening in fertility work-ups. An in vitro infection model of primary human Sertoli cells demonstrated that C. trachomatis can invade the seminiferous epithelium, induce cytoskeletal rearrangements and potentially compromise the blood-testis barrier, suggesting a mechanism for impaired spermatogenesis despite limited bacterial egress. Contrastingly, combined in vitro and animal-model studies reported that direct exposure of spermatozoa to C. trachomatis did not alter motility, viability or fertility indices, indicating that indirect inflammatory pathways rather than direct bacterial cytotoxicity may underlie chlamydial effects on male fertility.

Sexually Transmitted Infections and Male Fertility publication trend

The graph below shows the total number of articles in sexually transmitted infections and male fertility across all publications each year (not limited to Nature Index journals).

Technical terms

Semen parameters: Quantitative and qualitative measures of ejaculate including volume, sperm concentration, motility and vitality.

Sperm morphology: Assessment of sperm head, midpiece and tail structure to determine the proportion of normally shaped spermatozoa.

Oxidative stress: Imbalance between reactive oxygen species production and antioxidant defences, leading to cellular damage.

Reactive oxygen species (ROS): Highly reactive molecules derived from oxygen that can damage lipids, proteins and DNA.

Sertoli cells: Somatic cells in the seminiferous tubules that support and nourish developing germ cells and maintain the blood-testis barrier.

Blood-testis barrier: Physical and immunological barrier formed by tight junctions between Sertoli cells, protecting germ cells from systemic immune responses.

References

1. Effects of Ureaplasma urealyticum infection on semen quality and sperm morphology. Frontiers in Endocrinology (2023).
2. Genital mycoplasma infection: a systematic review and meta-analysis. Reproductive Health (2023).
3. Chlamydia trachomatis neither exerts deleterious effects on spermatozoa nor impairs male fertility. Scientific Reports (2017).
4. Results from a large cross-sectional study assessing Chlamydia trachomatis, Ureaplasma spp. and Mycoplasma hominis urogenital infections in patients with primary infertility. Scientific Reports (2021).
5. Growth kinetics of Chlamydia trachomatis in primary human Sertoli cells. Scientific Reports (2019).
6. Viral Infections and Male Infertility: A Comprehensive Review of the Role of Oxidative Stress. Frontiers in Reproductive Health (2022).
7. Asymptomatic seminal infection of herpes simplex virus. Journal of Biomedical Research (2012).
8. Proinflammatory and Oxidative Stress States Induced by Human Papillomavirus and Chlamydia trachomatis Coinfection Affect Sperm Quality in Asymptomatic Infertile Men. Medicina (2021).