A rare case of Cardiobacterium valvarum infective endocarditis in a pediatric patient with a history of truncus arteriosus repair

ABSTRACT Background Infective endocarditis (IE) in children is rare, and in North America it is most often associated with congenital heart disease and Gram-positive organisms. Bacteria belonging to the HACEK group account for a small minority of cases; Cardiobacterium valvarum is an exceptionally uncommon cause, with no previously reported pediatric cases. Case Summary A 6-year-old female with a history of repaired truncus arteriosus presented to the hospital with fever and polyuria. Urine cultures were negative; however, multiple sets of blood cultures grew a fastidious Gram-negative bacillus after 48 h. Echocardiography demonstrated an increased right ventricle-to-pulmonary artery conduit gradient and valvular thickening, raising concern for IE. Repeated identification attempts using Bruker Biotyper matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) in multiple laboratories and the BD Phoenix automated identification system were unsuccessful. Definitive identification was achieved by 16S rRNA gene sequencing, confirming the organism as Cardiobacterium valvarum . The patient was treated with 6 weeks of intravenous ceftriaxone, resulting in clearance of bacteremia. Subsequently, she underwent surgical conduit replacement with removal of valve vegetations and has remained clinically stable at 1 year follow-up. Conclusion This is the first reported case of pediatric IE caused by C. valvarum and highlights the diagnostic challenges associated with the organism. Limitations of MALDI-TOF MS may delay identification, and 16S rRNA sequencing may be critical for accurate diagnosis. Increased awareness of this rare pathogen is essential to guide management of pediatric IE.