Infectious and Commensal Bacteria in Rheumatoid Arthritis-Role in the Outset and Progression of the Disease.

Rheumatoid arthritis (RA) is a chronic, autoimmune disease with a complex outset. Besides the genetic susceptibility in its pathogenesis, various environmental factors also participate. Of these, in recent years, there have been increasing reports of the involvement of bacteria in the disease's outset and development, especially gut microbiota and oral pathogens. Most recent reports about bacteria participation in RA pathogenesis focus on Prevotella copri and Porphyromonas gingivalis. There are also reports about the involvement of respiratory and urinary tract pathogens. The exact mechanisms leading to RA development used by bacteria are not well known; however, some mechanisms by which bacteria can interact with the immune system are known and can potentially lead to RA development. The aim of this study is to provide a comprehensive review of the potential bacteria participating in RA development and the mechanism involved in that process.