A case report of chronic Q fever infection centred around prosthetic material after surgical treatment of Coxiella burnetii endocarditis: specialist multi-disciplinary input is essential

Coxiella burnetii causes chronic Q fever that often presents as culture-negative infective endocarditis (IE) and has a particular affinity for prosthetic material. Relapse despite apparently adequate therapy remains a therapeutic and diagnostic dilemma.

A young adult with repaired congenital aortic valve disease underwent urgent aortic root replacement with a mechanical valve conduit for culture-negative IE. Broad-range 16S rRNA polymerase chain reaction on the explanted prosthesis detected C. burnetii. He received 18 months of doxycycline-hydroxychloroquine, which was then stopped. Six months later, he was clinically well, but surveillance serology showed markedly elevated phase I/II IgG titres; ¹⁸F-FDG PET-CT demonstrated avid uptake circumferentially around the composite graft and a femoral arterial closure device, fulfilling major criteria for prosthetic valve IE. Given the prohibitive risk of redo sternotomy and stable haemodynamics, combination therapy was re-instituted with close monitoring. He has remained well on prolonged suppressive treatment.

This case highlights (i) the tendency of C. burnetii to persist on prosthetic material, (ii) the utility, and limitations of PET-CT in assessment of prosthetic valve endocarditis (especially Dacron), and (iii) the need to interpret C. burnetii serology appropriately, specifically the importance of testing serial samples in parallel. Our management aligns with the UK national Q fever MDT approach (UKHSA/RIPL) to favour prolonged medical therapy with structured clinical and serological review, considering step-down to suppressive doxycycline monotherapy, if appropriate, after 18–24 months. Lifelong serological surveillance is critical and medical suppression may be preferable to high-risk redo surgery in the absence of significant haemodynamic lesions.