Shared and distinct gut microbiota in spondyloarthritis, acute anterior uveitis, and Crohn's disease

OBJECTIVES: Spondyloarthritis (SpA) is a group of immune-mediated diseases highly concomitant with non-musculoskeletal inflammatory disorders, such as acute anterior uveitis (AAU) and Crohn's disease (CD). The gut microbiome represents a promising avenue to elucidate shared and distinct underlying pathophysiology. METHOD: We performed 16S rRNA sequencing on stool samples of 277 patients (72 CD, 103 AAU, and 102 SpA) included in the German Spondyloarthritis Inception Cohort (GESPIC) and 62 back pain controls without any inflammatory disorder. Discriminatory statistical methods were used to disentangle microbial disease signals from one another and a wide range of potential confounders. Patients were naïve to or had not received treatment with biological disease-modifying anti-rheumatic drugs for >3 months before enrollment, providing a better approximation of a true baseline disease signal. RESULTS: We identified a shared, immune-mediated disease signal represented by low abundances of Lachnospiraceae taxa relative to controls, most notably Fusicatenibacter, which was most abundant in controls receiving NSAID monotherapy and implied to partially mediate higher serum CRP. Patients with SpA showed an enrichment of Collinsella, while HLA-B27+ individuals displayed enriched Faecalibacterium. CD patients had higher abundances of a Ruminococcus taxon, and previous csDMARD therapy was associated with increased Akkermansia. CONCLUSION: Our work supports the existence of a common gut dysbiosis in SpA and related inflammatory pathologies. We reveal shared and disease-specific microbial associations and suggest potential mediators of disease activity. Validation studies are needed to clarify the role of Fusicatenibacter in gut-joint inflammation, and metagenomic resolution is needed to understand the relationship between Faecalibacterium commensals and HLA-B27