A 52-year-old man with a history of pulmonary tuberculosis (treated 5 years ago) presents with a 2-month history of progressive dyspnea and chest pain. High-resolution CT chest shows multiple nodules in both lungs with mediastinal lymphadenopathy. Transbronchial biopsy reveals caseating granulomas with acid-fast bacilli (AFB) on Ziehl-Neelsen stain. Sputum smear microscopy is negative for AFB. What is the most appropriate next step in management?