Most common cause of reactive arthritis?
S. flexneri(Ref. Harrison's Principles of Internal Medicine 16th Edition pg. 1996)
Reactive arthritis (ReA) refers to acute nonpurulent arthritis complicating an infection elsewhere in the body. In recent years, the term has been used primarily to refer to spondyloarthritides following enteric or urogenital infections and occurring predominantly in individuals with the histocompatibility antigen HLA-B27. In the setting of HIV infection, the association with B27 is not necessarily found. Other forms of reactive and infection-related arthritis not associated with B27 and showing a different spectrum of clinical features, such as rheumatic fever or Lyme disease.
Etiology and Pathogenesis
a. Of the four Shigella species S. sonnei, S. boydii, S. flexneri, and S. dysenteriae, S. flexneri has most often been implicated in cases of ReA, both sporadic and epidemic.
b. Other bacteria identified definitively as triggers of ReA include several Salmonella spp., Y. enterocolitica, C. jejuni, and C. trachomatis.
c. There is evidence implicating several other microorganisms, including Y. pseudotuberculosis, Clostridium difficile, and Ureaplasma urealyticum.