A 60-year-old man presents with an erythematous, warm, tender area over his left lower leg of 24 hours' duration. There is no abscess or purulent discharge. He is febrile to 38.2 °C but haemodynamically stable with no systemic toxicity and no risk factors for MRSA. According to Therapeutic Guidelines, which is the most appropriate oral antibiotic choice for this non-purulent cellulitis managed in the community?