Necrotizing Pneumonia Complicated by Bartonella-Associated Culture-Negative Endocarditis in an Immunocompetent Adult.

Bartonella-related culture-negative endocarditis (CNE) is an infrequent and difficult diagnosis, due to the organism's unique growth characteristics and frequent negative cultures. We describe a case of a 42-year-old previously healthy male with necrotizing pneumonia complicated by empyema and bronchopleural fistula. Despite signs of systemic inflammation and infection, multiple blood cultures remained negative. Our diagnosis was made with serologic testing, which revealed elevated Bartonella antibody levels, and echocardiographic findings of endocarditis. Bartonella species are zoonotic, time-dependent, Gram-negative bacteria most often transmitted by arthropod vectors. Cats often serve as reservoirs of the organism. Because of ambiguous clinical manifestations, early recognition is challenging unless there is initial suspicion of a zoonotic etiology. We hope this case emphasizes thinking of Bartonella and other zoonotic pathogens in CNE when routine cultures do not provide a diagnosis. Serologic testing and imaging studies are invaluable in the diagnostic process. Rapid identification and the use of appropriate antimicrobial therapy are essential to avoid significant complications and improve patient care.