Gut microbiota analysis revealed unique biomarkers in Ankylosing Spondylitis and Non-radiographic Axial Spondyloarthritis.

Objectives: In this paper, the different characteristics of gut microbiota between Ankylosing Spondylitis (AS), Healthy Control (HC), and Non-radiographic Axial Spondyloarthritis (nr-axSpA) were studied. The AS-nr-axSpA differentiation model was constructed to identify patients with these two phenotypes and help doctors make accurate diagnosis.

Methods: Stool samples and blood samples of AS, nr-axSpA, and HC were collected from our hospital. Bacterial lipopolysaccharides and lipopolysaccharides-binding proteins in blood were detected by enzyme-linked immunosorbent assay (ELISA). The V3-V4 region of bacterial 16SrRNA was analyzed by MiSeq PE300 sequencing platform with high throughput. Software such as QIIME, R, Excel, etc. were used for statistical analysis of the data. Random Forest (RF) and Area Under Curve (AUC) methods were used to construct the AS-nr-axSpA differentiation model and identify relevant important markers. Set markers and use the receiver operating characteristic curve (ROC) to judge the accuracy of the model.

Results: We studied a total of 59 fecal and corresponding blood samples from 31 AS, 21 nr-axSpA, and 7 HC. There was a significant difference in intestinal α diversity between AS and nr-axSpA patients (Shannon index, P = 0.017). Compared to the nr-axSpA patient population, Streptococcus (P = 0.045), Actinomyces (P = 0.0028), Rothia (P = 0.042), and Oribacterium in the intestinal tract of AS patients P = 0.044) increased significantly. However, Dorea (P = 0.034) and Odoribacter (P = 0.043) were significantly reduced. The AS-nr-axSpA model was constructed using 18 factors including Actinomyces and Odoribacter. ROC analysis was performed on the model and an ROC curve was drawn, with an AUC of 0.78, which is moderate accurate.

Conclusions: The gut microbiota of patients with AS differs from that of patients with nr-axSpA. The disturbance of gut microbiota may be one of the conditions for the progression of nr-axSpA to AS. The characteristics of gut microbiota and related bacterial products may serve as characteristic factors for differentiating the phenotypes of these two diseases. The AS-nr-axSpA model may help doctors distinguish patients with different phenotypes, but more robust prospective and standardized studies are needed to confirm these findings.