Bacterial communities in semen from men of infertile couples: metagenomic sequencing reveals relationships of seminal microbiota to semen quality.

Shun-Long Weng,Chih-Min Chiu,Chao Liang,Hsien-Da Huang,Wei-Yun Wu,Tzu-Ling Yang,Tzu-Hao Chang,Chia-Yu Liu,Ting Yang,Feng-Mao Lin,Yi-An Chang,Wei-Chih Huang,Zaid Abdo

doi:10.1371/journal.pone.0110152

Abstract

Some previous studies have identified bacteria in semen as being a potential factor in male infertility. However, only few types of bacteria were taken into consideration while using PCR-based or culturing methods. Here we present an analysis approach using next-generation sequencing technology and bioinformatics analysis to investigate the associations between bacterial communities and semen quality. Ninety-six semen samples collected were examined for bacterial communities, measuring seven clinical criteria for semen quality (semen volume, sperm concentration, motility, Kruger's strict morphology, antisperm antibody (IgA), Atypical, and leukocytes). Computer-assisted semen analysis (CASA) was also performed. Results showed that the most abundant genera among all samples were Lactobacillus (19.9%), Pseudomonas (9.85%), Prevotella (8.51%) and Gardnerella (4.21%). The proportion of Lactobacillus and Gardnerella was significantly higher in the normal samples, while that of Prevotella was significantly higher in the low quality samples. Unsupervised clustering analysis demonstrated that the seminal bacterial communities were clustered into three main groups: Lactobacillus, Pseudomonas, and Prevotella predominant group. Remarkably, most normal samples (80.6%) were clustered in Lactobacillus predominant group. The analysis results showed seminal bacteria community types were highly associated with semen health. Lactobacillus might not only be a potential probiotic for semen quality maintenance, but also might be helpful in countering the negative influence of Prevotella and Pseudomonas. In this study, we investigated whole seminal bacterial communities and provided the most comprehensive analysis of the association between bacterial community and semen quality. The study significantly contributes to the current understanding of the etiology of male fertility.

Highlights

Semen quality and male infertility Infertility is an increasingly common condition, and the male factors are estimated playing a significant role in about 40%–50% of infertile couples
Other potent noninfection causes such as vasovasostomy, varicoceles, autoimmunity, defective spermatogenesis and poor sperm viability can lead to elevated seminal leukocytes [10,11]
The results showed that the bacterial community could be clustered in to six group, and no significant differences were found between sperm donors and the infertility patients

Summary

Introduction

Semen quality and male infertility Infertility is an increasingly common condition, and the male factors (either alone or in combination with female factors) are estimated playing a significant role in about 40%–50% of infertile couples. Acute and chronic infections of the genitourinary (GU) tract may induce male factor infertility. Infectious etiologies cause about 15% of male factor infertility cases [4]. There are multiple causes of elevated seminal leukocytes (ESL) including infectious etiologies like genital-urinary infection and non-infectious etiologies including exposure to environmental toxins, man-made products during intercourse, tobacco products, alcohol and certain medications [9]. Other potent noninfection causes such as vasovasostomy, varicoceles, autoimmunity, defective spermatogenesis and poor sperm viability can lead to elevated seminal leukocytes [10,11]. Bacteriospermia and the recruitment of seminal leukocytes can potentially impair male fertility through the deterioration of spermatogenesis, impairment of sperm function, and genital tract dysfunction and/or obstruction

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Results

Conclusion