Metagenomic analysis of intestinal microbiota characteristic differences between patients with ankylosing spondylitis and healthy individuals

To explore the differences in intestinal microbiota between patients with ankylosing spondylitis (AS) and healthy individuals (HC) in terms of genetic, species composition, and functional levels, and to reveal the role of intestinal microorganisms in the pathogenesis of AS. This study selected 17 AS patients (AS group) and 17 healthy subjects (HC group) from the Affiliated Hospital of Liaoning University of Traditional Chinese Medicine between August to October 2024. Basic clinical data, as well as the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Visual Analogue Scale (VAS) score, of the AS group, were collected. Fresh fecal samples were also collected for metagenomic sequencing. Differences in microbiota were analyzed using methods including Alpha diversity analysis, species abundance analysis, Principal Coordinates Analysis (PCoA), Non-metric Multidimensional Scaling (NMDS), DESeq2 analysis, Linear Discriminant Analysis Effect Size (LEfSe), and Kyoto Encyclopedia of Genes and Genomes (KEGG) functional annotation. The number of unique genes in the AS group (566,526) was higher than that in the HC group (406,609). At the species level, there were no significant differences in Alpha diversity or the overall microbial structure (revealed by PCoA and NMDS) between the two groups (p > 0.05). However, significant differences in abundance were observed at the family, genus, and species levels. DESeq2 identified a total of 43 differential species, among which 22 species had increased abundance and 21 species had decreased abundance in the AS group. LEfSe analysis showed that the HC group had 16 dominant bacterial species, while the AS group had only Neoporus faecalis as the dominant species. There were differences in KEGG Level 3 functional pathways between the two groups, but no statistically significant difference was found in the overall functional structure (p = 0.698). Functional enrichment analysis revealed that AS-specific genes were primarily enriched in neurodegenerative disease pathways, protein processing in the endoplasmic reticulum, and autophagy-related pathways, with substantial contributions from genera including Bacteroides, Streptococcus, Eubacterium, and Faecalibacterium. However, neither individual differential species nor their functional pathways showed significant correlations with clinical disease activity scores (BASDAI and VAS)。. The studies indicated that although there was no significant difference in the overall diversity of intestinal microbiota between AS patients and healthy individuals, there were obvious distinctions in genetic composition, specific bacterial species, and functional pathways, suggesting that intestinal microorganisms may be involved in the pathogenesis of AS.