Molecular detection of Coxiella burnetii in the sera of patients with Q fever endocarditis or vascular infection.
In the absence of a specific diagnosis based on serology, chronic Q fever is inevitably fatal. However, diagnosis is often delayed because the test is not widely available. To shorten the diagnostic delay, we adapted a nested-PCR assay with serum as a template and the LightCycler as a thermal cycler, termed LCN-PCR. We retrospectively and prospectively applied this method to samples from 48 patients diagnosed with Q fever endocarditis or vascular infection and to samples from 100 controls with endocarditis caused by other microorganisms. We also prospectively applied this technique to samples from 30 patients treated for a Q fever endocarditis and to samples from 13 patients with a convalescent acute Q fever with ambiguous immunoglobulin G (IgG) phase I titer. LCN-PCR had a specificity of 100%. It was positive only in samples from patients with evolutive Q fever, as none of the samples from patients with a treated chronic Q fever or with a convalescent acute Q fever presented positive results. When performed prospectively on recently stored sera, the sensitivity of LCN-PCR is 64% (7 of 11 samples; P = 0.004), but the efficiency of LCN-PCR was dramatically altered by the storage of specimens at -20 degrees C. High IgG phase I titers decreased the sensitivity of LCN-PCR. A significant difference was observed among LCN-PCR results for sera with IgG phase I titers of > or =1:25,600 compared to sera with IgG phase I titers of <1:25,600 (0 of 15 samples versus 13 of 33 samples; P = 0.004). In patient samples with titers below 1:25,600 tested prospectively, sensitivity was 100% (7 of 7). The LCN-PCR assay may be helpful in establishing an early diagnosis of chronic Q fever.
Fenollar
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F
Unité des rickettsies, IFR 48 CNRS UMR 6020, Faculté de médecine, Université de la Méditerranée, 27 Boulevard Jean Moulin, 13385 Marseille cedex 5, France.
Fournier
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PE
Raoult
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D
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000907:Antibodies, Bacterial / Q000097:blood; D002908:Chronic Disease; D016997:Coxiella burnetii / Q000235:genetics / Q000302:isolation & purification*; D004269:DNA, Bacterial / Q000097:blood*; D004697:Endocarditis, Bacterial / Q000175:diagnosis / Q000382:microbiology*; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction / Q000379:methods; D011446:Prospective Studies; D011778:Q Fever / Q000175:diagnosis / Q000382:microbiology*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014652:Vascular Diseases / Q000175:diagnosis / Q000382:microbiology
D000907:Antibodies, Bacterial; D004269:DNA, Bacterial; D007074:Immunoglobulin G