A Case of Native Valve Infective Endocarditis and Bacteremia Due to Streptococcus cristatus

Infective endocarditis is a severe infection affecting the inner lining of the heart chambers and valves, often preceded by bacteremia and frequently caused by organisms from the commensal oral flora, including Streptococcus (S.) cristatus. However, S. cristatus remains an uncommon causative agent. We present the case of a 68-year-old male with a history of dyslipidemia, severe aortic insufficiency, and mild mitral insufficiency who presented with a two-week history of fever without other symptoms. Blood cultures were positive for Streptococcus cristatus, and a transthoracic echocardiogram revealed multiple vegetations on the aortic valve and smaller vegetations on the mitral valve. Additionally, splenic embolization was detected. The patient was treated with benzylpenicillin and gentamicin, followed by aortic valve replacement surgery. This case highlights a previously immunocompetent patient who developed bacteremia and fulfilled the definitive criteria for infective endocarditis, characterized by severe aortic valve insufficiency and splenic embolization, caused by a commensal oral bacterium rarely reported in clinical cases. The severity of the infection necessitated surgical intervention, and the patient subsequently made a full recovery without major complications post-discharge.