The 5-Month Mystery

A 62-year-old man with a history of severe aortic stenosis presents to the emergency department with 3 weeks of progressive illness. He initially developed low-grade fevers at home, which he attributed to "post-viral fatigue." Over the past week, he has noticed increasing fatigue, decreased exercise tolerance, and night sweats that soak through his pillow. He also reports decreased appetite and an unintentional 3-kg weight loss.

Five months prior, he underwent a successful surgical aortic valve replacement with a bioprosthetic valve for severe symptomatic aortic stenosis. His postoperative course was uncomplicated, and he has been in regular follow-up. He denies any recent dental procedures, surgery, invasive procedures, or catheterizations. His only medication is aspirin 81 mg daily.

On arrival, his temperature is 38.2°C, heart rate is 92/min, blood pressure 128/70 mmHg, respiratory rate 18/min, and oxygen saturation 98% on room air. Physical examination reveals a thin, somewhat diaphoretic man in mild distress. Cardiac auscultation demonstrates a new soft diastolic murmur at the right upper sternal border, different from his postoperative exam. He has no peripheral stigmata of endocarditis. No jugular venous distension or peripheral edema is noted.

Laboratory evaluation shows a white blood cell count of 11.2 x 10^9/L (neutrophils 78%, lymphocytes 12%, monocytes 8%), hemoglobin 10.8 g/dL, platelets 245 x 10^9/L, C-reactive protein 45 mg/dL, and erythrocyte sedimentation rate 68 mm/hour. Basic metabolic panel reveals creatinine 1.1 mg/dL, blood urea nitrogen 22 mg/dL, and normal electrolytes. Urinalysis shows trace protein but no hematuria or pyuria.

Three sets of blood cultures drawn more than 1 hour apart all grow gram-positive cocci in clusters after 48 hours of incubation. The laboratory performs a coagulase tube test, which shows the patient's isolate fails to clot plasma after 24 hours (negative), while a control staphylococcal isolate shows clot formation within 4 hours (positive). Gram stain confirms gram-positive cocci in clusters. Oxacillin susceptibility testing is pending, but the isolate is presumed methicillin-resistant pending full susceptibilities. Initial transthoracic echocardiography is limited by body habitus and prosthetic valve shadowing, with inconclusive findings for vegetation or abscess.