system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
A 13-year-old boy is brought to the emergency department because of a 2-day history of fever, headache, and irritability. He shares a room with his 7-year-old brother, who does not have any symptoms. The patient appears weak and lethargic. His temperature is 39.1°C (102.4°F) and blood pressure is 99/60 mm Hg. Physical examination shows several purple spots over the trunk and extremities. A lumbar puncture is performed. Gram stain of the cerebrospinal fluid shows numerous gram-negative diplococci. Administration of which of the following is most likely to prevent infection of the patient's brother at this time?
assistant
Rifampin