A 62-Year-Old Man with a History of Coronary Artery Disease

A 62-year-old man with a history of coronary artery disease comes to the emergency department with 2 days of fever and fatigue.  Over the last 24 hours, he has developed progressive fatigue and confusion.  The patient's past medical history is notable for a coronary catheterization 2 weeks ago with placement of an intracoronary stent in the right posterior descending artery.  He was discharged home within 24 hours.  He has no other medical history or prior surgeries.  The patient lives in New York with his wife, who has been well.  He has no recent travel and currently works as an accountant.
On physical examination, the patient appears uncomfortable but is clinically stable.  His temperature is 38.6 C (101.5 F) , blood pressure is 122/70 mm Hg, and pulse is 114/min and regular.  There is no lymph node enlargement.  There is no tenderness to palpation over the sinuses.  The lungs are clear on auscultation.  No heart murmurs are appreciated.  The abdomen is soft and nontender.  The tip of the spleen is not palpated.  There is no rash.  Laboratory results are as follows:

He is initially treated with vancomycin and piperacillin-tazobactam.  Forty-eight hours later, blood cultures from admission grow methicillin-resistant Staphylococcus aureus.
What is the best next step in management of this patient's infection?

A) Add gentamicin
B) Add rifampin
C) Colonoscopy
D) Echocardiogram
E) Ophthalmologic examination