Coxiella burnetii, a gram-negative, obligate intracellular bacterium, causes the zoonotic disease Q fever in humans, manifesting in both acute and chronic forms. Domestic animals and livestock are the primary reservoirs. C. burnetii is distributed worldwide, with 460 cases in the European Union in 2021. Vascular graft infections by C. burnetii are rare but they are linked to significant morbi-mortality. C. burnetii is known for causing culture-negative vascular infections in pathological arteries, valves, and vascular grafts. Negative cultures can lead to inefficient antibiotic therapy and catastrophic clinical outcomes.

We report a case of chronic Q fever in a 76-year-old male patient with a history of prosthetic aorto-bifemoral and venous femoro-popliteal bypass of the right leg, along with multiple endovascular revisions for peripheral arterial disease (PAD). In 2022, he underwent a Silvergraft prosthetic interposition between the two bypasses for a pseudo-aneurysm. In November 2023, he presented with a right femoral wound dehiscence and active bleeding. At admission, leucocytes were 16.2 G/l and C-Reactive Protein (CRP) 2.2 mg/l. Urgent surgery revealed an anastomotic bleeding with a strong suspicion of infection. The interposition graft was replaced with an Omniflow graft, and Co-Amoxicillin was started empirically.

Initial bacteriological cultures were negative, and PET-CT showed no vascular hypercaptation. The patient was never febrile. Due to infectious clinical suspicion with unidentified etiology, the infectious diseases department suggested the implementation of C. burnetii serologies, which came back positive for IgG phase I and II antibodies. A long-term Doxycycline and Plaquenil treatment was initiated. Subsequent wound closure was achieved after 10 days of vacuum-assisted (VAC) therapy. Due to distal popliteal occlusion, the patient underwent an allograft bypass between the femoro-popliteal bypass and the peroneal artery 3 months later. No new infections were diagnosed.

In patients with high suspicion of vascular graft infection and negative cultures, serology for C. burnetii should be performed. Here, we discuss the multidisciplinary approach and surgical strategies - focusing on critical aspects of microbiology, imaging, and treatment – that led to good outcomes in this challenging case.