Pneumocystis jirovecii (Pneumocystis pneumonia)

A 65-year-old man comes to the emergency department for evaluation of three weeks of a dry cough, shortness of breath, and fever. The patient has noted significant weight loss (10 lb) over the last nine months. Past medical history is significant for dyslipidemia, HIV, and CMV retinitis. The patient is noncompliant with antiretroviral therapy. Current medications include tenofovir-emtricitabine and dolutegravir and atorvastatin. The patient is sexually active with men and uses condoms inconsistently. The patient does not use intravenous drugs, alcohol, or tobacco. The patient owns two parrots and a cat. Temperature is 38.11°C (100.0°F), pulse is 121/min, respirations are 26/min, and blood pressure is 98/75 mmHg, SpO₂ is 89% on room air. The patient is using accessory muscles of respiration. Physical examination reveals anterior and posterior cervical lymphadenopathy. Oral examination reveals white, mucosal plaques on the lateral aspect of the tongue that cannot be scraped off with a tongue depressor. Rales are present in the bilateral anterior lung fields. A CT of the patient’s chest is depicted below.  CD4 count is 157 cells/microL. Which of the following organisms is the most likely etiology of this patient’s current disease process?
 
^Radiopedia