Several species of bacteria, including Chlamydia trachomatis and, less frequently, Chlamydophila (Chlamydia) pneumoniae, are known to trigger reactive arthritis. Although the effectiveness of long-term antibiotic therapy in patients with reactive arthritis is controversial, these two organisms exist in a state of persistent, metabolically active infection in the synovial tissue, thus rendering them particularly susceptible to antimicrobial agents. A study by Carter et al. investigated whether a 6-month course of combination antibiotics is effective in patients with chronic, Chlamydia-induced reactive arthritis.

The prospective, multicenter, double-blind, placebo-controlled study included 42 patients (57% men, mean age 45.9 years) with mean disease duration >10 years. Participants were randomly allocated to receive doxycycline plus rifampicin (n = 12), azithromycin plus rifampicin (n = 15), or placebos (n = 15). Use of additional long-term medications (corticosteroids, NSAIDs, DMARDs and biologic agents) was permitted.

The primary outcome measure—≥20% improvement in at least 4 out of 6 variables (swollen and tender joint counts and 4 questionnaire components assessing low-back morning stiffness, low-back and peripheral pain, and global disease activity) without worsening of any variables—was achieved in 17 (63%) of 23 patients receiving active treatment versus 3 (20%) of 15 patients in the placebo group (P = 0.01). At 6 months, 5 of the 6 variables had improved considerably from baseline in the active treatment groups, compared with none in the placebo group.

The authors conclude that combination antibiotic therapy can potentially eradicate persistent Chlamydia infection in these reactive arthritis patients. Further study is needed to find the optimal antibiotic combination and dosing regimen in this setting.