Molecular Detection of Coxiella burnetii in the Sera of Patients with Q Fever Endocarditis or Vascular Infection

Abstract

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°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 >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.

The Q fever epidemic in The Netherlands: history, onset, response and reflection

“…Infection in pregnancy may lead to adverse pregnancy outcomes, such as spontaneous abortion or premature delivery. About 1-5 % of all Q fever cases may progress into a chronic infection, often leading to life-threatening endocarditis [4,[6][7][8][9].…”

Antimicrobial peptides as new recognition molecules for screening challenging species

“…The key advantages of ELISA are its overall sensitivity and the lack of requirement for significant sample preparation. PCR, on the other hand, is generally more sensitive and specific and, once nucleic acids are extracted, rapid; a number of excellent, high sensitivity PCR-based assays have been described [4][5][6][7][8][9][10][11]. However, both antibody-and nucleic acid-based detection methods require prior development of target-specific reagents whose efficacy is highly dependent on assumed genetic sequences and/or antigenic motifs.…”

First genetic evidence of Coxiella burnetii in cases presenting with acute febrile illness, India

“…Serum samples that were found positive by both techniques were further tested by nested PCR targeting repetitive element IS1111 of C. burnetii [25] aiming to amplify a 520 bp fragment in the first amplification and a 297 bp fragment in the second. Four samples tested positive by nested PCR.…”