A 7-year-old girl presents with a 1-day history of fever, sore throat and difficulty swallowing. She has a temperature of 39.0 °C, tender anterior cervical lymphadenopathy and tonsillar exudates but no cough. A rapid antigen test for group A streptococcus is not available. She has no allergies. What is the most appropriate management according to Australian antibiotic guidelines?