P-092 Interaction of male and female genital microbiota in infertile couples undergoing assisted reproductive technology
Authors: Peric A , Vidal A , Weiss J , Baud D , Stojanov M 
Published: June 2023

Abstract

Study question
Is there a crosstalk between the male and female genital microbiota of couples undergoing assisted reproductive technology (ART) and the outcome of this treatment.

Summary answer
Despite the presence of bacteria linked with bacterial vaginosis in male samples, there appears to be very limited impact on the microbiota of female partners.

What is known already
In recent years, thanks to advancements in sequencing technologies, the microbiota has been explored extensively and many of its roles in human physiology were deciphered. Compared to its female counterpart, male genital microbiota has been understudied. Presence of bacteria in sperm was generally associated with a pathological condition, but recent reports indicate that the male genital tract is colonized by bacteria and even good quality semen generally contains bacteria. Previously three main semen microbiota profiles were identified, two of these were composed of bacteria, usually found in the vagina, indicating that bacteria could be shared between partners during sexual intercourse.

Study design, size, duration
Prospective observational study including 65 couples receiving ART between 2018 and 2020 at a single fertility center in Switzerland, to investigate the interaction of male and female reproductive tract microbiota. Samples were collected by swabbing penile skin and seminal fluid as well as vagina and follicular fluid.

Participants/materials, setting, methods
Samples of 64 infertile couples undergoing ART were collected by direct sampling (vagina and penis glans) or by immersion in the biological fluid (follicular fluid and semen). Follicular fluid was obtained during oocyte pick-up. Sampling of vagina and penis glans (self-sampling) as well as immersion of semen was performed on the same day.
16S rRNA profiling (next generation sequencing) was used to characterize bacterial populations in the samples using a previously developed pipeline.

Main results and the role of chance
Lactobacillus spp. were highly prevalent in follicular fluid samples and especially in vaginal samples. Generally, penis glans samples were highly colonized by different bacteria and showed the highest alpha diversity. Follicular fluid and semen samples had generally low bacterial biomass. Lactobacillus iners was the most prevalent species in female samples. This is also the case for male samples, although the abundance was lower.
For male patients, comparison of beta diversities showed that intra-individual samples were more similar compared to same sample types from different individuals. The opposite was observed for vaginal samples, where inter-individual differences were less marked compared to samples of the same woman. Similar analyses were performed to evaluate relatedness of samples from the same couple, allowing us to estimate the possible impact of microbiota interaction between partners. Despite generally high values, in several cases intra-couple dissimilarities were significantly lower when compared to same sample type of different individuals.
Analysis of differently abundant taxa showed, as expected, that Lactobacillus genus was enriched in female samples, along with Atopobium spp. A higher number of genera was specifically enriched in male samples, including Prevotella, Campylobacter and Mobiluncus genera among others.

Limitations, reasons for caution
Limitations of this study are, that it is only observational and the number of patients included is relatively small.

Wider implications of the findings
Our results suggest a very limited impact of male microbiota on the female bacterial colonization, despite male samples were enriched with bacterial genera negatively associated with reproduction. Future analysis of the influence of sexual activity on the microbial composition should comprise samples obtained before and after sexual intercourse.

Trial registration number
not applicable