Native Aortic Valve Endocarditis Caused by Rothia mucilaginosa, Initially Misidentified as Neisseria sicca

BACKGROUND Infective endocarditis is a potentially life-threatening disease predominantly affecting the heart valves. Common causative pathogens include Staphylococcus aureus and Streptococcus viridans. However, it can be caused by atypical organisms such as Rothia species (spp.). When Rothia spp. cause endocarditis, the organism often affects prosthetic valves and rarely native ones. We report a case of native aortic valve subacute endocarditis caused by R. mucilaginosa, initially misidentified as Neisseria sicca, in an immunocompromised middle-aged patient. CASE REPORT A 54-year-old man with histories of hemochromatosis, diabetes, hypertension, alcohol abuse, and smokeless tobacco use presented with 7 days of fever, intermittent cough, and headache. Diagnostic workup revealed a new systolic murmur, blood cultures positive for N. sicca, and a vegetation on the aortic valve noted on a transesophageal echocardiogram. He was diagnosed with subacute infective endocarditis using Duke criteria and discharged on 6 weeks of intravenous ceftriaxone. However, 1 day later, he presented to another facility with a new fever and had a chest X-ray showing atypical pneumonia. The initial blood isolates were re-identified as R. mucilaginosa. His hospital course was complicated by a small intraparenchymal hemorrhage and 2 embolic infarcts. He continued ceftriaxone and eventually recovered to baseline. CONCLUSIONS We present a case of an immunocompromised middle-aged man who developed subacute infective endocarditis caused by an atypical organism, R. mucilaginosa. Infective endocarditis should always be a differential diagnosis in patients presenting with fever of an unknown source.