Analysis of risk factors for malignant Mediterranean spotted fever indicates that fluoroquinolone treatment has a deleterious effect.

OBJECTIVES: To identify risk factors for malignant Mediterranean spotted fever (MSF) caused by Rickettsia conorii conorii.

PATIENTS AND METHODS: Epidemiological, clinical and biological characteristics as well as risk factors (including treatment regimens) for severe MSF cases were analysed retrospectively. A patient with two or more organ dysfunctions or patient death was defined as a severe case.

RESULTS: During the study period (January 1999 to December 2009), 161 MSF cases were referred to our centre for rickettsioses. Twenty-six cases (16.1%) were considered severe, which is 3-fold higher than in our previous studies. The clinical and laboratory findings were comparable to those reported elsewhere except that the type of antibiotic treatment was associated with disease severity. Doxycycline administration prior to deterioration of disease (in 31 patients) protected patients from development of severe MSF [relative risk (RR) 0.248, 95% confidence interval (CI) 0.08-0.76] and induced earlier defervescence compared with the other treatment regimens (3.02 ± 2.2 days versus 7.1 ± 6.57 days, P = 0.021). In contrast, fluoroquinolone treatment (in 21 patients) was significantly and independently associated with MSF severity (RR 2.53, 95% CI 1.40-4.55) and was associated with a significantly longer hospital stay.

CONCLUSIONS: In this retrospective study fluoroquinolone treatment was associated with increased MSF disease severity. Fluoroquinolones have been previously associated with treatment failure in typhus and scrub typhus cases. Thus, we do not recommend the use of fluoroquinolones to treat rickettsial diseases.