Microbiomes in Sexual and Gender Minority Populations: Anatomy, Identity, Exposure and Clinical Outcomes

Microbiome studies in lesbian, gay, bisexual, transgender and other sexual and gender minority populations encompass partner-associated ecology, gender-affirming care, infection and prevention. This critical narrative review integrates human evidence by sex assigned at birth, gender identity and expression, sexual orientation and practices, current anatomy, and clinical state. Prevotellaceae-enriched intestinal profiles recur in several MSM cohorts, with geographical, behavioral and HIV-related heterogeneity. Female-partner studies capture both stable Lactobacillus-associated communities and transitions toward bacterial vaginosis. Testosterone-exposed vaginas and surgically reconstructed genital tissues show different relationships between composition, symptoms and inflammation; direct neovaginal testing demonstrates poor diagnostic performance of Nugent scoring. Oral, urinary, seminal and fungal studies broaden the clinical scope, while separately analyzed gender-expression, nonbinary and asexual evidence remains sparse. Intervention findings further distinguish microbial modulation from clinical benefit: resistance determinants can increase without broad taxonomic change, and a dietary trial links baseline community features to exploratory metabolic response. The comparative synthesis identifies tissue, endocrine state and measured endpoint as central to interpreting microbial markers. Clinical translation requires longitudinal exposure contrasts, expressed-function measurements and trials with validated patient-important outcomes.