A 28-year-old woman from Delhi presents to the emergency department with acute onset sore throat, fever (39.2°C), and dysphagia for 2 days. On examination, she has exudative pharyngitis with enlarged tonsils, petechial rash on the soft palate, and cervical lymphadenopathy. A rapid antigen detection test (RADT) for group A Streptococcus is positive. She has no drug allergies. What is the most appropriate immediate next step in management?