This prospective cohort study profiled gut microbiota (full-length 16S rRNA, PacBio) in 39 azoospermic men (OA n=14, NOA n=25) and evaluated whether microbial signatures were associated with successful sperm retrieval after microdissection testicular sperm extraction (mTESE).
NOA patients had reduced Bacteroidota (23.5% vs 28.5%, p<0.001) and elevated Proteobacteria (9.7% vs 3.8%, p<0.001) vs OA. Within NOA, successful retrieval (52%, 13/25) was linked to a higher Firmicutes-to-Bacteroidota ratio (AUC 0.76; 76.9% sensitivity, 75.0% specificity at cutoff ≥2.20) and enrichment of *Finegoldia magna* (AUC 0.756; 100% specificity at abundance ≥8.7%, though sensitivity was only 46.2%).
- Small sample (n=39 total; n=25 NOA) limits statistical power and generalizability. - Single timepoint 16S rRNA sequencing cannot assess functional capacity (no metagenomics or metabolomics) or temporal stability of microbiota. - Single Taiwanese tertiary center cohort; ROC cutoffs are hypothesis-generating only, with no external validation.
Gut microbiota profiling is not ready for clinical use in NOA counseling, but these exploratory findings suggest the Firmicutes-to-Bacteroidota ratio and *Finegoldia magna* abundance warrant further study as non-invasive correlates of mTESE success. Clinicians should await validation in larger, multicenter cohorts before applying any microbiota-based thresholds.
