A 48-year-old woman presents to her primary care provider's office with a two-week history of worsening fatigue, general malaise, and intermittent low-grade fevers, often peaking in the late afternoon. She recalls a routine dental cleaning approximately six weeks prior but denies any recent intravenous drug use, significant past medical history, or chronic cough. On physical examination, her temperature is 38.3 C, blood pressure is 130/70 mm Hg, pulse is 88/min, and respiratory rate is 16/min. Subtle reddish-brown streaks are noted beneath the nail beds of several fingers, and a new early diastolic murmur is audible along the left sternal border. Petechiae are observed on her conjunctiva. Pulmonary auscultation reveals clear breath sounds bilaterally, and abdominal examination is benign. Given these findings, what is the most likely diagnosis and the appropriate initial empiric treatment strategy?

A 55-year-old man presents to the emergency department reporting 3 days of worsening fever, malaise, and new-onset confusion. He underwent a transcatheter aortic valve replacement (TAVR) four weeks ago and has been recovering at home. His temperature is 39.1 C, blood pressure is 118/68 mm Hg, pulse is 110/min and regular, and respiratory rate is 20/min. On physical examination, he appears lethargic but is arousable. Cardiac auscultation reveals a regular rhythm with a grade II/VI systolic ejection murmur previously noted but no new or changing murmurs. Lungs are clear to auscultation. There are no petechiae or splinter hemorrhages. Abdomen is soft, non-tender, and bowel sounds are normal. Laboratory results are pending. Considering the patient's presentation, what is the most likely diagnosis and the appropriate initial empiric antimicrobial regimen and key diagnostic step?

A 46-year-old woman presents to her primary care physician with a 6-week history of intermittent low-grade fevers, progressive fatigue, and generalized malaise. She reports recent tooth sensitivity and gum bleeding, which she attributes to delayed dental care. On physical examination, a 2/6 holosystolic murmur is auscultated at the cardiac apex. Further evaluation with transthoracic echocardiography reveals a 6-mm mobile vegetated mass attached to the anterior leaflet of the mitral valve, without significant valve dysfunction. Blood cultures performed on two separate occasions yield Eikenella corrodens. Given these findings, what is the most appropriate diagnosis and the recommended initial antimicrobial therapy for this patient?