A 62-year-old man presents to the emergency department because of new symptoms of fevers, chills, and malaise. His past medical history is significant for a prosthetic aortic valve replacement 5 years ago because of aortic stenosis from a bicuspid valve.On physical examination, the blood pressure is 130/85 mm Hg, heart rate is 88/min, and temperature 38.5degC. He has a 2/6 systolic ejection murmur heard best at the aortic region and a mechanical second heart sound, but no other abnormalities on examination. Blood cultures are most likely to grow which of the following?