A 58-year-old man presents with erythema, warmth and tenderness of his left lower leg extending from the ankle to mid-calf, with low-grade fever. There is no fluctuance or abscess. He has no systemic toxicity. According to Therapeutic Guidelines: Antibiotic, what is the most appropriate empirical oral antibiotic for this non-purulent cellulitis in an adult without MRSA risk factors?