Q. A 61-year-old woman comes to her physician three months after a root canal. She states that during the six weeks after her root canal, she started experiencing general fatigue, malaise, and an ongoing, low-grade fever. She called for an appointment when her granddaughter told her that her eyes, “looked gross.” The patient presents with a temperature of 100.4°F. Ophthalmic examination reveals retinal hemorrhages with clear central regions. She has painful, red nodules on her fingers and toes with dark macules on her palms and soles. Cardiac auscultation reveals a click and a mitral valve systolic murmur. When asked about this, she informs the physician that the click is from a mechanical valve replacement done four years ago. Which of the following is the most appropriate treatment?