Review Question - QID 214706

A 48-year-old man presents to the emergency department with 2 weeks of progressive dyspnea and pain on inspiration in his left chest. He was treated for pneumonia by his primary care physician 1 week prior. The patient states he took the full course of antibiotics. He has diabetes that is well-controlled with diet. His surgical history is significant for a kidney transplant 3 years prior. He takes tacrolimus daily. He has no known allergies. He smokes half a pack of cigarettes per day. His temperature is 102.4°F (39.1°C), blood pressure is 116/78 mmHg, pulse is 108/min, and respirations are 22/min. On physical exam, the patient is alert and oriented. Cardiac examination demonstrates normal S1 and S2 with no murmurs, rubs, or gallops. Pulmonary examination demonstrates dullness to percussion in the lower left lung field. There is no evidence of edema in the bilateral lower extremities. A chest CT scan demonstrates a large, loculated pleural fluid collection on the left side. Laboratory results are as follows:

Serum:
Leukocyte count: 18,000/mm^3
Total serum protein: 7 g/dL
Serum LDH: 100 U/L

Pleural Fluid Analysis:
pH: 7.0
Glucose: 38 mg/dL
Leukocyte count: 80,000/mm^3
Protein: 5 g/dL
LDH: 70 U/L
Gram stain: Positive

Which factor is the etiology of the patient's condition?