The gut microbiome is distinct in people with Crohn’s disease, and even axial compared to peripheral spondyloarthritis.
People with Crohn’s disease and associated joint inflammation have changes in their gut microbiome, prompting hopes that one bacterium could become a new biomarker.
Researchers found that patients with Crohn’s disease and either axial or peripheral spondyloarthritis had higher rates of Mediterraneibacter gnavus bacteria coated with the antibody IgG in their gut compared to healthy controls or those with Crohn’s disease and no joint inflammation.
Up to one in three patients with Crohn’s disease may also experience joint inflammation, author Associate Professor Randy Longman, a US gastroenterologist and mucosal immunologist, told media.
“While joint inflammation is one of the most common extraintestinal manifestations of Crohn’s disease, clinicians don’t have a good handle on why this happens and how to treat it,” he said.
Professor Longman and colleagues analysed stool and serum samples from around 100 US patients, 39 with Crohn’s disease and peripheral spondyloarthritis, 14 with Crohn’s and axial spondyloarthritis, 44 with Crohn’s but no joint inflammation and nine healthy controls.
“This unique cohort revealed distinct taxonomic compositions of CD and CD-SpA compared to healthy controls and demonstrates that the composition of the CD-AxSpA microbiome is distinct from that of CD-pSpA,” the authors wrote.
They found IgG-coated M. gnavus in 33% of patients with Crohn’s disease and peripheral spondyloarthritis, 29% of those with Crohn’s disease and axial spondyloarthritis and only 11% in Crohn’s disease without inflammation and healthy controls.
IgG helps the body fight off pathogens and triggers inflammation. The level of IgG coating found in the samples was associated with disease activity scores in patients with joint inflammation.
“The research also raises the possibility that there could be a causative link between the gut microbiota and immune cell responses that govern inflammation, but further investigation is needed,” Professor Longman said.
The authors said it was still unclear what parts of the bacteria the immune system was reacting to.
“Ultimately, I hope to figure out how to target or otherwise mitigate the effect of these bacteria on joint inflammation in patients with Crohn’s disease,” said study co-author Dr Grace Maldarelli, a US infectious disease specialist.
