Q. A 45-year-old man comes to the emergency department due to a fever of two weeks duration. The patient's medical history is significant for diabetes, hypertension, and two previous attacks of infective endocarditis. He recently visited a dentist to remove an impacted third molar. The patient is currently enrolled in an addiction support group and has abstained from heroin injections since his enrollment five months ago. Vital signs show a low-grade fever. Cardiac auscultation reveals a holosystolic murmur over the mitral region. Infection is suspected. Which of the following is the most likely causative organism for the patient’s condition?