Streptococcus viridans Quiz: Ace Your Exams

A 63-year-old man presents to the primary care physician with a 6-week history of malaise, chills, and fevers. He additionally has had a 4.5-kg (10-lb) weight loss over this same time period. His past medical history is significant for hypertension, hyperlipidemia, as well as a known mitral valve prolapse. The patient reports he has otherwise been in his usual state of health and endorses compliance with his home medication regimen. He has a past surgical history of total hip replacement at 61, as well as a molar tooth extraction two months ago. Temperature is 37.7°C (99.8°F), pulse is 80/min, respirations are 20/min, and blood pressure is 135/85 mmHg. Physical examination is notable for a 3/6 holosystolic murmur present at the apex that radiates to the left axilla. Blood is drawn and sent for culture. Three days later, 3 of 4 blood cultures obtained on admission grow Gram-positive, alpha-hemolytic bacteria. Which of the following is the most likely pathogen implicated in this patient’s disease process?