Abstract
Kingella kingae, a rare member of the Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, and Kingella (HACEK) group, is an uncommon cause of infective endocarditis (IE) in adults. Advances in molecular diagnostics, including polymerase chain reaction (PCR) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), have significantly improved its identification. We present the case of a 78-year-old immunocompromised woman who developed watershed territory cerebral infarctions in the setting of K. kingae endocarditis. The patient initially presented with fever, altered mental status, and right-sided weakness and was later found to have K. kingae bacteremia, as well as a 7 mm aortic valve vegetation. Due to high surgical risk, the patient was managed conservatively with long-term intravenous antibiotics. This case highlights how modern diagnostic tools facilitate early detection of atypical pathogens and allow for more timely non-surgical management in vulnerable populations.