A 52-year-old woman with a prosthetic aortic valve (bioprosthetic, inserted 8 years ago for aortic stenosis) presents with fever, night sweats, and progressive fatigue for 6 weeks. On examination, blood pressure is 145/55 mmHg with a wide pulse pressure. A new early diastolic murmur is heard at the left sternal border. Blood cultures grow viridans group streptococci (penicillin-susceptible). Transoesophageal echocardiography (TEE) shows a 6 mm vegetation on the aortic valve with mild aortic regurgitation and no dehiscence. What is the most appropriate management strategy?