Researchers from the University of Leeds and Leeds Teaching Hospitals NHS Trust found that bacteria linked to inflammation in the gut in higher amounts about 10 months before patients develop clinical rheumatoid arthritis.

The findings may help identify people at risk and also pave the way for preventive and personalised treatment strategies, said the team.

To better understand, the researchers followed 124 people at risk of developing rheumatoid arthritis for 15 months. Of these 7 were newly diagnosed and 22 were healthy. The changes in the gut microbiome profiles were assessed using stool and blood samples at 5 different time points.

The presence of precursor anti-cyclic citrullinated protein (anti-CCP) antibodies - which attack healthy cells and are specific for rheumatoid arthritis - and joint pains in the preceding 3 months were identified as the major risk factors.

During the study period, 30 of the 124 in the at-risk group progressed to rheumatoid arthritis. Compared to the healthy comparison group, their microbial diversity also was reduced.

Recognised genetic, blood, and imaging risk factors for arthritis development were also significantly linked to lower microbial diversity, as was steroid use.

Among people who progressed to rheumatoid arthritis, and those who are newly diagnosed a specific strain of Prevotellaceae sp - (ASV2058) most likely Prevotella Copri - was found to be abundant.

Another strain (ASV1867) of P copri was also increased at the start of the study, suggesting that the gut bacteria might play a role in rheumatoid arthritis progression, the researchers said.

"Individuals at risk of [rheumatoid arthritis] harbour a distinctive gut microbial composition, including but not limited to an overabundance of Prevotellaceae species. This microbial signature is consistent and correlates with traditional risk factors,” said the research published online in the Annals of the Rheumatic Diseases.

While the findings suggest that changes in the gut microbiome are a late-stage phenomenon, it is an observational study and warrants more studies.