Treatment of Chronic Q Fever: Clinical Efficacy and Toxicity of Antibiotic Regimens.

Background: Evidence on the effectiveness of first-line treatment for chronic Q fever, tetracyclines (TET) plus hydroxychloroquine (HCQ), and potential alternatives is scarce.

Methods: We performed a retrospective, observational cohort study to assess efficacy of treatment with TET plus quinolones (QNL), TET plus QNL plus HCQ, QNL monotherapy, or TET monotherapy compared to TET plus HCQ in chronic Q fever patients. We used a time-dependent Cox proportional hazards model to assess our primary (all-cause mortality) and secondary outcomes (first disease-related event and therapy failure).

Results: We assessed 322 chronic Q fever patients; 276 (86%) received antibiotics. Compared to TET plus HCQ (n = 254; 92%), treatment with TET plus QNL (n = 49; 17%), TET plus QNL plus HCQ (n = 29, 10%), QNL monotherapy (n = 93; 34%), or TET monotherapy (n = 54; 20%) were not associated with primary or secondary outcomes. QNL and TET monotherapies were frequently discontinued due to insufficient clinical response (n = 27, 29% and n = 32, 59%). TET plus HCQ, TET plus QNL, and TET plus QNL plus HCQ were most frequently discontinued due to side effects (n = 110, 43%; n = 13, 27%; and n = 12, 41%).

Conclusions: Treatment of chronic Q fever with TET plus QNL appears to be a safe alternative for TET plus HCQ, for example, if TET plus HCQ cannot be tolerated due to side effects. Treatment with TET plus QNL plus HCQ was not superior to treatment with TET plus HCQ, although this may be caused by confounding by indication. Treatment with TET or QNL monotherapy should be avoided; switches due to subjective, insufficient clinical response were frequently observed.