Rоxаnne, а 23-yeаr-оld medical student, arrives in the student health clinic cоmplaining of difficulty in swallowing, sore throat, and chills. Upon examination, she is found to be running a fever, and has white patches on her tonsils. A throat swab is positive for Streptococcus pyogenes (group A). A diagnosis of acute pharyngitis is made. Her past medical history is unremarkable except for an anaphylactic reaction to cefaclor two years ago. Which of the following would be a safe alternative for treating Roxanne's condition?