A 64-year-old man with type 2 diabetes and COPD has fever, pleuritic chest pain and productive cough for 4 days. He was admitted 3 weeks ago for a foot ulcer. CXR shows left lower lobe consolidation with a pleural effusion. Thoracentesis: turbid fluid, pH 7.12, LDH 1100, WBC 18,000 (neutrophils). Gram stain pending. What is the next step?