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Microbes may be implicated in rheumatoid arthritis

Published online 6 August 2015

Rheumatoid arthritis may soon benefit from microbial-based diagnosis and therapies.

Nadia El-Awady

Rheumatoid arthritis (RA) is an autoimmune disease that is most known for causing chronic inflammation of the joints. It affects tens of millions of people worldwide and is associated with increased death rates.

Its exact causes are unclear, but both genetic and environmental factors are thought to be involved, including the possibility of a microbial link. 

A large team of scientists from China, together with a colleague from King Abdulaziz University in Saudi Arabia, conducted gene analyses to determine the microbial contents of the guts and mouths of people with RA. Faecal, saliva and dental samples were taken from 77 people with untreated RA and compared with samples from 80 healthy individuals.

They found microbial imbalances in the mouths and guts of people with RA that were partially resolved after they received treatment. These imbalances were significant enough to distinguish RA patients from healthy ones and to categorize them on the basis of their responses to treatment.  

The team found that looking for genetic markers of specific gut and mouth microbes, such as Lactobacillus salivarius or Haemophilus, was an efficient way to diagnose RA. It also can be done by people for themselves, because taking swabs from the thin film that covers teeth and taking saliva samples is easy. 

The findings are a first step toward potential microbial-based diagnosis, prognosis and treatment of rheumatoid arthritis and similar autoimmune diseases. 


Zhang, X. et al. The oral and gut microbiomes are perturbed in rheumatoid arthritis and partly normalized after treatment. Nature Medicine (2015)