Blood Culture–Negative Legionella TAVR Endocarditis

BACKGROUND: Legionella endocarditis is exceedingly rare and diagnostically challenging. We present the first confirmed case of blood culture-negative Legionella cardiaca prosthetic valve endocarditis (PVE). CASE SUMMARY: A 77-year-old man with prior transcatheter aortic valve replacement presented with 8 months of daily fevers, malaise, and unintentional weight loss. Serial blood cultures were negative. Multimodality imaging suggested transcatheter aortic valve replacement-PVE, with significant valvular obstruction. Plasma microbial cell-free DNA sequencing detected Legionella species, prompting targeted therapy. The prosthetic valve was explanted, and histopathology revealed numerous bacilli. Broad-range 16S rRNA sequencing confirmed Lcardiaca. DISCUSSION: This case highlights the diagnostic complexity of culture-negative Legionella PVE and the value of multimodality imaging and molecular techniques for accurate diagnosis and management. TAKE-HOME MESSAGES: Multimodality imaging plays an integral role in the diagnosis of infective endocarditis. Molecular diagnostics should be considered early in blood culture-negative endocarditis, particularly when conventional microbiologic testing is unrevealing.