Most common organism associated with reactive ahritis is
Staphylococcus
Shigella
Chlamydia
Yersinia
Reactive (spondylo)ahritis (ReA) is a 'reaction' to a number of bacterial triggers with clinical features in keeping with all SpA conditions. The known triggers are Chlamydia, Campylobacter, Salmonella, Shigella and Yersinia. Notably, non-SpA-related reactive ahritis can occur following infection with many viruses, Mycoplasma, Borrelia, streptococci and mycobacteria, including M. leprae, which causes leprosy (Hansen's disease); however, the 'reaction' in these instances consists typically of myoahralgias, is not associated with HLA-B27 and is generally not chronic. The ahritis associated with rheumatic fever is also an example of a reactive ahritis that is not associated with HLA-B27.Sexually acquired reactive ahritis (SARA) is predominantly a disease of young men, with a malepreponderance of 15 : 1. This may reflect a difficulty in diagnosing the condition in young women, in whom Chlamydia infection is often asymptomatic and is hard to detect in practical terms. Between 1% and 2% of patients with non-specific urethritis seen at genitourinary medicine clinics have SARA. The syndrome of chlamydial urethritis, conjunctivitis and reactive ahritis was formerly known as Reiter's disease. Ref Davidsons 23e p1031
Immune system