A 52-year-old man with chronic obstructive pulmonary disease (COPD) presents with acute exacerbation: productive cough with purulent sputum, fever (38.5°C), and dyspnea. Chest X-ray shows bilateral interstitial infiltrates. Sputum culture and PCR are pending. Empiric treatment for community-acquired pneumonia (CAP) is initiated. What is the preferred antibiotic regimen for suspected atypical pneumonia (including Chlamydia pneumoniae) in this outpatient COPD patient?