Asymptomatic bacteriospermia and infertility—what is the connection?

Objective To determine the impact of asymptomatic bacteriospermia on semen quality in subfertile men. Methods We conducted a retrospective, single-centre cohort study in 1300 subfertile men. In those diagnosed with asymptomatic bacteriospermia we performed univariate and multivariate logistic regression models to evaluate the strain-specific association with semen parameters. Results Asymptomatic bacteriospermia was diagnosed in 3.2% of patients. The microbiological semen analysis revealed a poly-microbial result in 60%. The most common bacterial species were coagulase-negative Staphylococci species (71.4%), Streptococcus viridans (50.0%) and Enterococcus faecalis (26.2%). Sexually transmitted pathogens were identified in 11.9% of semen samples. The detection of Streptococcus viridians or Haemophilus parainfluenzae correlated with impaired sperm morphology ( p < 0.05). The presence of coagulase-negative Staphylococci species or Enterococcus faecalis was associated with pathological low counts of live spermatozoa ( p < 0.05). In multivariate analysis only Enterococcus faecalis showed a significant impact on sperm concentration (OR 4.48; 95% CI 1.06–22.10; p = 0.041). Conclusions Asymptomatic bacteriospermia has always been a subject of great controversy. There is still an ongoing debate whether to treat or not to treat. Here, we demonstrate that asymptomatic bacteriospermia is clearly associated with impaired semen quality. Our findings speak in favour of strain-specific interactions with semen parameters. Especially Enterococcus faecalis seriously affects sperm concentration.