A 47-year-old woman who underwent hematopoietic stem cell transplantation for acute lymphoblastic leukemia 3 months ago presents to the emergency department with a 3-day history of cough, dyspnea, fever, and shortness of breath. She has no reported comorbidities. Her post-transplant course includes the administration of colony-stimulating factors for prolonged neutropenia. On examination, her temperature is 38.4 °C (101.2 °F), pulse is 101/min, respiratory rate is 19/min, blood pressure is 130/90 mm Hg, and SpO2 is 95% on room air. Physical examination reveals bilateral pulmonary crackles. A chest CT scan demonstrates bilateral nodules, consolidative lesions, and the “halo sign.”

Which of the following is the pathogen most likely responsible for her condition?