Semen Microbiota are Dramatically Altered in Men with Abnormal Sperm Parameters

There has recently been an explosion of studies implicating the human microbiome in playing a critical role in many disease and wellness states. The etiology of abnormal semen analysis (SA) parameters is not identified in 30% of cases; investigations involving the semen microbiome may bridge this gap. Here, we explore the relationship between the semen microbiome and alterations of sperm parameters. We recruited men presenting for fertility evaluation or vasectomy consultation with proven biological paternity. Men with abnormal sperm motility (N=27) showed a higher abundance of Lactobacillus iners (p=0.0464) compared to those with normal sperm motility (N=46). This relationship persisted on canonical correlational analysis (r=0.392, p=0.011). Men with abnormal sperm concentration (N=20) showed a higher abundance of Paraburkholderia phenazinium, Pseudomonas fluorescens, and Pseudomonas stutzeri, but a lower abundance of Pseudomonas putida (all p<0.05), compared to those with normal sperm concentration (N=53). Major limitations are related to study design (cross-sectional, observational). Our results suggest that a small group of microorganisms may play a critical role in observed perturbations of SA parameters. Some of these microbes, most notably Lactobacillus iners, have been described extensively within other, fertility-related, contexts, whereas for others, this is the first report where they have potentially been implicated.