Review Question - QID 217059

A 48-year-old woman presents to the emergency department with fever. She has been having fever and chills for the past 7 days. She also has associated malaise, body aches, and night sweats. She has a history of mitral stenosis but is otherwise healthy. She takes no medications. She received a root canal 1 month ago but has no other prior surgeries. She smokes 1 pack of cigarettes a day and has been doing so for 20 years. She denies illicit drug use. She immigrated from India several months ago. Her temperature is 102.6°F (39.2°C), blood pressure is 110/70 mmHg, pulse is 102/min, and respirations are 22/min. On physical exam, her lung fields are clear to auscultation. There is a 2/6 rumbling, diastolic murmur auscultated over the apex. Urinalysis and a chest radiograph are negative. A leukocytosis and elevated lactate are noted on lab testing. Blood cultures are currently pending. Which of the following is the most likely cause of this patient's symptoms?