Review Question - QID 214890

A 39-year-old woman presents to the emergency department with a 1-week history of fever, cough, night sweats, and chest pain. She says that she began to develop the symptoms after she returned from a road trip vacation across the United States but cannot think of any particular trigger. Her past medical history is significant for polymyositis for which she is on chronic prednisone suppression. Chest radiographs reveal multifocal consolidation and further testing with an acid-fast stain reveals the results shown in Figure A. A purified protein derivative (PPD) test reveals no erythema or induration. Which of the following is most likely the cause of this patient's symptoms?