Molecular detection of Coxiella burnetii in blood and sera during Q fever

Abstract

Sir, We read with interest the intriguing article by Marmion et al. 1 which describes the molecular detection of Coxiella burnetii in two cohorts of patients from Australia and the UK, 5 years and 12 years after initial infection, respectively. Their data suggest that C. burnetii DNA may persist up to 12 years in blood of patients who are eventually cured, or those suffering only from fatigue. Moreover, authors found that PCR targeting single-copy genes such as Com 1 and 16S rRNA genes, wase more sensitive than that targeting the 1S1111a repetitive element.2 According to these authors, PCR targeting 1S1111a was negative in the UK cohort, presumably due to the absence of these insertion elements in the strain of C. burnetii that was the causative agent of Q fever in this patient population. In our opinion, such a notion is conjecture, since C. burnetii was not isolated from any of the patients in the UK cohort. Indeed, we routinely used in our laboratory a real-time quantitative PCR assay with Taqman probe targeting the IS1111 a and IS30a repetitive elements for the diagnosis and follow-up of patients with Q fever either in biopsies or in blood and sera,3,,4 and we never obtained such results. From March 2004 to April 2005, we have tested blood and sera of 546 patients with strict PCR conditions4 and clear definitions of clinical cases.5,,6 Using our primers and probes targeting these two genes, among the 546 patients being tested we have obtained 34 positive PCR in blood and/or sera (6.2%). Among these 34 positive patients, 22 patients had active acute Q fever, six had active Q-fever endocarditis, four had a vascular infection, one had spondylodiscitis, and one was a pregnant woman with Q fever infection, confirmed by culture …