Pneumonia USMLE Step 1 Practice Question

A 62-year-old man with poorly controlled type 2 diabetes mellitus presents to the emergency department with a 3-day history of fever, productive cough with purulent sputum, and progressive dyspnea. He denies recent hospitalization or antibiotic use. Vital signs show temperature 39.2°C, blood pressure 142/88 mmHg, heart rate 108/min, respiratory rate 22/min, and SpO2 94% on room air. Physical examination reveals dullness to percussion and bronchial breath sounds over the right lower lobe. Chest X-ray shows a right lower lobe consolidation with a characteristic bulging fissure sign. Gram stain of sputum demonstrates gram-negative rods that appear mucoid. Which of the following organisms is most likely responsible for this patient's pneumonia?