Melioidosis Presenting as a Mycotic Aneurysm of the Aortic Arch in a Patient With Pyrexia of Unknown Origin: A Case Report

Melioidosis is an infection caused by the environmental saprophyte Burkholderia pseudomallei and is endemic to tropical regions. It has diverse clinical manifestations; however, vascular involvement in the form of a mycotic aneurysm is rare and associated with significant morbidity and mortality. We describe a 50-year-old male farmer from Kerala, India, with a nine-month history of recurrent fever, weight loss, and fatigue who underwent multiple admissions and exhaustive evaluation for pyrexia of unknown origin. Sequential blood cultures over this period identified a Pseudomonas species and a non-fermenting Gram-negative bacillus (NFGNB). A focal saccular outpouching at the distal aortic arch had been documented on a computed tomography scan two months before presentation to our institution, but was not initially pursued as a potential focus of infection. Fluorodeoxyglucose positron emission tomography subsequently localised abnormal uptake to this same aneurysm. Blood cultures at our institution, incubated for 10 days, grew B. pseudomallei. The patient became afebrile within 24 hours of initiating intravenous ceftazidime and underwent distal aortic arch replacement with a 20 mm Dacron graft and reimplantation of the subclavian arteries (7 mm each). The postoperative course was complicated by nosocomial sepsis due to carbapenem-resistant Klebsiella pneumoniae and ventilator-associated pneumonia, both of which resolved with targeted therapy. The patient completed eight weeks of ceftazidime-based intensive therapy and was discharged on oral cotrimoxazole eradication therapy. This case highlights several instructive issues: the recurrent misidentification of B. pseudomallei by conventional biochemical identification methods, the diagnostic utility of antibiogram pattern recognition, the role of fluorodeoxyglucose positron emission tomography in pyrexia of unknown origin, the importance of considering any saccular aortic aneurysm as potentially mycotic, and the limitations of applying the 2023 Duke-International Society for Cardiovascular Infectious Diseases criteria to an extracardiac vascular infection.