Bacteriology USMLE Step 1 Practice Question

A 67-year-old man with a 10-day history of productive cough, fever, and dyspnea is admitted to the hospital. He has a history of COPD but denies recent aspiration, dental procedures, or immunosuppression. Vital signs: temperature 39.1°C, heart rate 105/min, respiratory rate 23/min, blood pressure 132/78 mmHg, oxygen saturation 91% on room air. Physical examination reveals dullness to percussion and decreased breath sounds in the right lower lobe. Chest X-ray shows a cavitary lesion with an air-fluid level in the right lower lobe consistent with lung abscess. Laboratory studies reveal WBC 15,400/μL with left shift. Sputum culture is pending but Gram stain shows gram-positive cocci in chains and gram-negative rods. Which of the following organisms is most likely to be isolated from this patient's sputum culture?