Which organism is most commonly associated with reactive arthritis?

Reactive arthritis is an inflammatory joint condition that typically occurs after an infection, often involving the genitourinary or gastrointestinal tracts. It is particularly associated with specific pathogens, and Chlamydia trachomatis is one of the most well-recognized organisms linked to this condition.

Chlamydia trachomatis can cause urethritis or cervicitis, and in susceptible individuals, this can trigger a reactive arthritis response, leading to joint inflammation, commonly in the knees and ankles. The association is notable because reactive arthritis is considered a type of spondyloarthritis, which links musculoskeletal symptoms to prior infections.

Other organisms listed may cause arthritis or other musculoskeletal conditions, but they are not primarily associated with reactive arthritis as Chlamydia is. Escherichia coli, for instance, is more commonly related to urinary tract infections and may rarely lead to inflammatory joint disease, but it does not have the same strong correlation with reactive arthritis. Streptococcus and Staphylococcus aureus are primarily linked to septic arthritis or acute infection rather than reactive arthritis following an infection. Hence, Chlamydia trachomatis stands out as the most common organism associated with reactive arthritis.