A Patient Was Initially Treated as an Outpatient for Pneumonia

A patient was initially treated as an outpatient for pneumonia and then after 2 weeks was hospitalized after no improvement was evident. The patient continues to show no improvement after several antibiotic regimens have been attempted. What is the next step in managing this patient?

A) Administration of the pneumonia vaccine
B) Increasing the dose of the antibiotics
C) Open lung biopsy
D) Performing diagnostic bronchoscopy