Q-Fever endocarditis: Prosthetic valve infection in the absence of zoonotic exposure.

Background: Q-Fever is a rare condition with an often insidious presentation. Endocarditis is a serious complication of up to 5% of Q-Fever cases, with a higher incidence and mortality in patients with prosthetic valves.Case-history: A 67-year-old man presented with a 6-weeks history of breathlessness on a background of previous bioprosthetic aortic valve replacement in 2018. Subsequent echocardiograms showed severe eccentric aortic regurgitation, a 2 cm vegetation, and severely impaired biventricular function. Routine blood cultures were negative, but later PCR testing for non-culturable microorganisms, performed due to the high probability of endocarditis, was positive for Coxiella Burnetii. The patient denied any recent constitutional symptoms and previous exposure to animal reservoirs. He underwent a successful urgent redo sternotomy and aortic valve replacement with a bioprosthesis. Prosthetic valve PCR testing was positive for Coxiella Burnetii, and he completed a long antibiotic course with follow-up serology to guide therapy. Clinic follow-up 3 months later showed good recovery with no complications.Conclusions: This case emphasises the high index of suspicion and routine screening needed in culture-negative cases to diagnose Q-Fever endocarditis, especially in the absence of acute symptoms and exposure to known sources of transmission. The complexities in management and timing of surgery are discussed.