Microbiota of the seminal fluid from healthy and infertile men

Abstract

Objective: To explore potential causes of male infertility by determining the composition and structure of commensal bacterial communities in seminal fluids.

Design: Microscopy of Gram-stained semen samples and classification of 16S rRNA gene sequences to determine the species composition of semen bacterial communities.

Setting: Clinical andrology laboratory and academic research laboratories.

Patient(s): Nineteen sperm donors and 58 infertility patients.

Intervention(s): None.

Main outcome measure(s): Classification of 16S rRNA gene sequences, clustering of seminal microbial communities, and multiple statistical tests.

Result(s): High numbers of diverse kinds of bacteria were present in most samples of both sperm donors and infertility patients. The bacterial communities varied widely among subjects, but they could be clustered into six groups based on similarities in composition and the rank abundances of taxa. Overall, there were no significant differences between sperm donors and infertility patients. However, multiple statistical tests showed a significant negative association between sperm quality and the presence of Anaerococcus. The results also indicated that many of the bacterial taxa identified in semen also occur in the vaginal communities of some women, especially those with bacterial vaginosis, which suggests that heterosexual sex partners may share bacteria.

Conclusion(s): Diverse kinds of bacteria were present in the human semen, but there were no significant differences between sperm donors and infertility patients. The presence of Anaerococcus might be a biomarker for low sperm quality.

Keywords: Semen; bacterial communities; fertility; microbiome; reproduction.

Copyright © 2013 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.

Figures

Figure 1

Gram stained semen samples from: semen donors NS8 and NS11 (panels a and b, respectively); (c) subject LM6 with asthenozoospermia; (d) subject OZ3 with oligoasthenozoospermia; (e) subject OZ13 with severe oligoasthenozoospermia; and (f) subject AS8 with azoospermia. The black arrows point to sperm and red arrows point to bacteria.

Figure 2

Hierarchical clustering of semen microbial communities in normal and infertile men and a heat map showing the proportions of various bacterial genera in each community. The sperm quality of each sample is indicated by the color-coded bar immediately below the dendrogram. Analysis of similarities in community composition and structure resulted in six clusters as indicated in the color bar below the heat map.