Objective To examine whether Coxiella burnetii (C. burnetii) is involved in chronic fatigue syndrome (CFS), we administered tetracycline antibiotics to subjects with CFS, and followed changes in clinical symptoms, PCR findings, and C. burnetii antibody titers. Patients and Methods The subjects were 8 patients with CFS and 213 with nonspecific complaints such as chronic fatigue and low-grade fever for several months or longer but not meeting the diagnostic criteria for CFS. All were examined for

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... C. burnetii infection by nested PCR and the indirect immunofluorescence test (IF). Results Four CFS patients (the CFS group) and 54 controls [the post-Q fever fatigue syndrome (QFS) group] positive for C. burnetii were treated mainly with minocycline or doxycycline (100 mg/day) for 3 months. After treatment, all 58 patients tested negative for C. burnetii infection. In the CFS group, no significant difference was noted between the mean pre-and post-treatment temperatures or headache scores. Similarly, there was no significant improvement in performance status (PS) scores. In the QFS group, however, mean temperatures and headache scores were significantly decreased after treatment (p<0.001). PS scores were also improved. Conclusion These results suggest the possibility of direct involvement of C. burnetii in the pathological state of CFS to be low, despite the C. burnetii infection rate being high in CFS patients. This is a pilot study and further larger investigations are necessary to confirm our preliminary results.