A 62-year-old man presents with erythematous, warm swelling of his left lower leg over 24 hours. He has a temperature of 38.2 °C, HR 92 bpm and BP 130/78 mmHg. There is a poorly demarcated area of erythema extending from ankle to mid-calf, with no abscess, necrosis or systemic toxicity. He has type 2 diabetes controlled on Metformin with no peripheral vascular disease. What is the most appropriate empirical oral antibiotic?