PLE-3644

A 19-year-old New York dirt bike racer, who recently raced for the first time in races along the Mississippi and also in the desert southwest, presents in September with cough, malaise, low-grade fever, myalgias, and chest pain. Rales are heard and respiratory infiltrates are noted on radiograph. Sputum stained with calcofluor white and viewed with an ultraviolet microscope shows hundreds of tiny yeast cells inside white cells. If cultured at room temperature, hyphae with small microconidia and tuberculate macroconidia would grow. What is the most likely causative agent?