A 54-Year-Old Woman Who Recently Received a Renal Transplant Comes

A 54-year-old woman who recently received a renal transplant comes to the emergency department due to fevers and malaise for the past 24 hours.  She also has had a cough productive of yellow sputum over the past 2 days.  No one around her has similar symptoms.
Three weeks ago, the patient underwent cadaveric renal transplant for long-standing renal disease.  Her immediate postsurgical course was uneventful, and she was extubated 3 days after surgery.  Her other medical problems include gastroesophageal reflux, hyperlipidemia, and eczema.
After the transplantation, she moved in with her sister, who had just donated her 2 cats to a local pet store.  The patient does not use tobacco or alcohol.  Her current medications include prednisone, tacrolimus, mycophenolate, valganciclovir, sulfamethoxazole/trimethoprim, pravastatin, and omeprazole.  She has no known drug allergies.
Her temperature is 38.5 C (101.3 F) , blood pressure is 130/80 mm Hg, pulse is 98/min, and respirations are 18/min.  Pulse oximetry shows oxygen saturation of 95% on room air.  Breath sounds are decreased in the left lung base with mild wheezing over the upper lung fields bilaterally.  Her abdomen is soft and nontender without a palpable spleen tip.  Neurologic examination is within normal limits.
Laboratory results are as follows:

Chest-x ray reveals a left lower lobe infiltrate.
Which of the following is the most likely cause of her condition?

A) Cytomegalovirus
B) Nocardia asteroides
C) Pasteurella multocida
D) Pneumocystis jirovecii
E) Pseudomonas aeruginosa