Q. A 67-year-old man is admitted to the hospital 12 days ago following a stroke. He was initially doing well, but his condition has deteriorated over the past three days. The nursing staff noticed that he has become progressively lethargic and less responsive. His daughter also reports a change in his behavior. On physical examination, he is febrile with a temperature of 38.7 °C (101.6 °F). His pulse rate is 108 beats per minute, blood pressure is 100/70 mmHg, and respiratory rate is 26 breaths per minute. There are crackles heard on auscultation over the right lower lung field. Laboratory investigations reveal a white blood cell count of 15,000/mm3, with a left shift. Chest X-ray shows a new right lower lobe infiltrate. Blood cultures are taken and sent to the lab. His arterial blood gases (ABGs) on room air show pH 7.34, PCO2 50 mmHg, PO2 65 mmHg, and bicarbonate 24 mEq/L. Considering the clinical presentation, what is the most appropriate next step of management in terms of initiating antibiotic therapy?