Metagenome-wide association study of the alterations in the intestinal microbiome composition of ankylosing spondylitis patients and the effect of traditional and herbal treatment

Introduction. Ankylosing spondylitis (AS) is a systemic progressive disease with an unknown etiology that may be related to the gut microbiome. Therefore, a more thorough understanding of its pathogenesis is necessary for directing future therapy. Aim. We aimed to determine the differences in intestinal microbial composition between healthy individuals and patients with AS who received and who did not receive treatment interventions. In parallel, the pathology of AS in each patient was analysed to better understand the link between AS treatment and the intestinal microbiota of the patients. Methodology. Sixty-six faecal DNA samples, including 37 from healthy controls (HCs), 11 from patients with untreated AS (NM), 7 from patients treated with nonsteroidal anti-inflammatory drugs (e.g. celecoxib; WM) and 11 from patients treated with Chinese herbal medicine (CHM), such as the Bushen-Qiangdu-Zhilv decoction, were collected and used in the drug effect analysis. All samples were sequenced using Illumina HiSeq 4000 and the microbial composition was determined. Results. Four species were enriched in the patients with AS: Flavonifractor plautii, Oscillibacter, Parabacteroides distasonis and Bacteroides nordii (HC vs. NM, P<0.05); only F. plautii was found to be significantly changed in the NM-HC comparison. No additional species were found in the HC vs. CHM analysis, which indicated a beneficial effect of CHM in removing the other three strains. F. plautii was found to be significantly increased in the comparison between the HC and WM groups, along with four other species (Clostridium bolteae, Clostridiales bacterium 1_7_47FAA, C. asparagiforme and C. hathewayi). The patients with AS harboured more bacterial species associated with carbohydrate metabolism and glycan biosynthesis in their faeces. They also had bacterial profiles less able to biodegrade xenobiotics or synthesize and transport vitamins. Conclusion. The gut microbiota of the patients with AS varied from that of the HCs, and the treatment had an impact on this divergence. Our data provide insight that could guide improvements in AS treatment.