A 32-year-old woman from Mumbai presents with 14 days of fever, myalgia, and diarrhea. Blood and stool cultures both grow Salmonella typhi. She is allergic to beta-lactams (documented anaphylaxis to penicillin). Her temperature is 39.2°C, and she is alert and oriented. Susceptibility testing shows the isolate is susceptible to fluoroquinolones and chloramphenicol but resistant to trimethoprim-sulfamethoxazole. What is the most appropriate next step in management?