Gut Microbiome Changes Different in Ankylosing Spondylitis and IBD, Associated With Disease Activity

The gut microbiome of patients with ankylosing spondylitis (AS) is distinct from that of patients with inflammatory bowel disease (IBD), according to study results presented at the American College of Rheumatology (ACR) Convergence 2020, held virtually from November 5 to 9, 2020. Researchers also noted that disease activity in both AS and IBD were correlated with changes in the gut microbiome.

Previous studies have confirmed that the gut and stool microbiome in AS and IBD are distinct from those of healthy individuals. Approximately 60% of patients with AS are estimated to have subclinical IBD and 5% to 10% have clinical IBD. The current study was aimed at characterizing the gut microbiome in AS and IBD and the relationship of the gut microbiome to disease activity in both diseases.

Researchers obtained stool samples, terminal ileal biopsies, colonic biopsies, and/or rectal biopsies from 192 patients with AS (5 with concomitant IBD [AS-IBD]), 59 patients with IBD, and 112 control participants, all of whom were undergoing routine colon cancer screening studies. Metagenomic profiling was performed using 16S ribosomal RNA sequencing. Alpha diversity, beta diversity, and taxonomies were compared between patient groups. Analyses were controlled for age, body mass index, country of origin, smoking status, sex, and tumor necrosis factor (TNF) inhibitor use. The area under the receiver operating characteristic curve (AUC) was used to assess the ability of the stool microbiome to distinguish between patient groups.

Alpha and beta diversity were found to be significantly different between the AS, AS-IBD, and IBD patient groups. Alpha and beta diversity differences between the AS and IBD groups persisted even after stratification by fecal calprotectin (FCP) levels (<100 vs >100 μg/mg). The stool microbiome could be used to accurately distinguish between patients with AS and AS-IBD, with an AUC of 0.754 that exceeded the AUC of the Dudley Inflammatory Bowel Symptom Questionnaire (0.716), an accepted means of identifying bowel symptoms in patients with AS. In addition, the stool microbiome accurately distinguished between patients with IBD from healthy control participants (AUC, 0.757). Among patients with AS, beta diversity, and not alpha diversity, differed between disease activity strata on the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI; P =.015).

Use of TNF inhibitors was associated with different gut microbiome profiles in patients with IBD. Finally, increased Haemophilus carriage was observed in patients with AS-IBD, patients with AS, particularly those with a BASDAI of 7.5 or greater, and patients with IBD with FCP greater than 100 μg/mg. Apart from Streptococcus and Haemophilus, no other indicator taxa were shared between the AS and IBD groups.  

These findings are “consistent with immunological and genetic evidence suggesting that the gut plays a different role in driving AS compared with IBD,” the researchers wrote. “[Patients] with AS and AS-IBD have a distinct gut microbiome compared with [patients] with IBD and healthy controls.”

Disclosure: A study author declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

Sternes P, Brett L, Phipps J, et al. Gut microbiome changes are different between ankylosing spondylitis and inflammatory bowel disease, and correlate with disease activity in both diseases. Presented at: ACR Convergence 2020; November 5-9, 2020. Abstract 1310.