Genital microbiota in infertile couples

Abstract

Research question: What is the composition of bacterial communities at various genital sites and are there potential interactions between partners' microbiota?

Design: This observational study involved metagenomic analyses of samples collected from male and female partners of couples undergoing fertility treatment. Samples included vaginal and penile swabs, as well as follicular fluid and semen, which were analysed using next-generation sequencing.

Results: The bacterial community profiles of different genital tract niches were distinct, niche-specific compositions, with female samples predominantly featuring Lactobacillus species and male samples displaying greater microbial diversity, including genital-specific and skin-associated taxa. Significant differences were observed between the sample types and intra-couple comparisons, which suggested potential microbiota interactions between partners. Differential abundance analyses further identified genera specifically enriched in female versus male samples, and correlations between partner samples point towards possible microbial transmission or shared influences on genital microbiota composition.

Conclusions: Despite advances in reproductive medicine, many infertility cases remain idiopathic, prompting exploration into how the genital microbiota (both in female and male reproductive tracts) might influence reproductive success. Our findings reveal that, although female samples were predominantly colonized by Lactobacillus species, particularly in the lower genital tract, male samples had greater microbial diversity (including bacteria linked to bacterial vaginosis), with only limited evidence of inter-partner microbiota transmission, underscoring the need for further longitudinal studies on the effect of sexual activity on microbial dynamics.

Keywords: Bacteria; Colonization; Lactobacillus; Microbiota; Semen; Vagina.