Review Question - QID 214818

A 47-year-old woman presents with fever, headache, and malaise for 2 weeks duration. Initially, she could control her headaches with acetaminophen, but now her “head is pounding” and she can hardly focus. The patient has a history of human immunodeficiency virus (HIV). She admits to taking her anti-viral medications inconsistently. Her temperature is 99.6°F (37.6°C), blood pressure is 110/70 mmHg, pulse is 92/min, and respirations are 17/min. Physical examination discloses pain with neck flexion. Her last CD4+ count was 84 cells/mm^3. A computed tomography (CT) of the head reveals multiple variably enhancing lesions. A lumbar puncture with mucicarmine staining reveals encapsulated organisms with red inner capsules and narrow budding. Which of the following is the most appropriate next step in management?