Infective Endocarditis (IE): Etiology von John Fisher, MD

Which of the following organisms is most likely to cause infective endocarditis with negative blood cultures?

Which of the following causes of infective endocarditis is NOT a member of the HACEK group?

Which of the following organisms is NOT a common cause of early or late prosthetic valve endocarditis?

A 71-year-old man comes to the physician because of fever, myalgias, low back pain, and increasing dyspnea on exertion for 10 days. Six weeks ago, he underwent aortic valve replacement for calcific aortic stenosis. On physical examination, he is pale and ill-appearing. A systolic ejection murmur which radiates into the carotids is present and inspiratory rales are audible at both lung bases. Four of four blood cultures are positive and aortic valve vegetations are present on echocardiography consistent with endocarditis. While many organisms could be associated, which of the following organisms is the most likely cause?