Microbial community structure and source contribution to the early neovaginal microbiota following penile inversion...

The process of colonization of the neovagina in the first year after surgical creation is largely unknown. We characterized the microbiota of the donor tissue sites that formed the neovagina, of the gut and of the neovagina itself to evaluate the source of the neovaginal microbiota.

Thirty transgender women assigned male at birth were included. Using 16S rRNA sequencing and aerobic culture, we analyzed the penile, scrotal, urethral and rectal microbiota before surgery, and the neovaginal microbiota in the period of 2 to 13 months after vaginoplasty.

Each of the sites was characterized by a specific microbiota. The neovagina was characterized by the second highest bacterial richness and diversity after the gut. The neovaginal microbiota was dominated by anaerobic bacteria of the phyla Firmicutes and Bacteroidota. The most abundant genera were Prevotella, Peptoniphilus, Anaerococcus and Porphyromonas. These genera, together with Dialister, Finegoldia and Actinomyces formed a neovaginal core microbiota, representing genera present in more than 50% of the samples, each with a minimum relative abundance of 1%. More than half of the neovaginal bacteria were not shared with the tissue sites that formed the neovagina. The site with the highest percentage of shared neovaginal Amplicon Sequence Variants (ASVs) was the gut, followed by the urethra. Complementary aerobic culturing showed that on average 38.7% of neovaginal bacterial species were shared with at least one other site.

The early neovaginal microbiota is highly diverse, dominated by anaerobic bacteria and is distinct from the microbiota of the tissue sites that form the neovagina. As most neovaginal ASVs are unshared, this indicates that bacteria from other environments may colonize the neovagina in this early period after creation of this new environment. These findings suggest implications for neovaginal health, potentially informing studies on probiotic therapies to support the colonization of the neovagina with beneficial bacteria.