Bacteriology USMLE Step 1 Practice Question

A 32-year-old woman presents to the emergency department with a 3-day history of fever, severe frontal headache, and neck stiffness. She reports photophobia and has had one episode of emesis. Vital signs: temperature 39.4°C, heart rate 112 bpm, blood pressure 116/74 mmHg, respirations 20/min. On examination, she has a positive Kernig sign and Brudzinski sign. Lumbar puncture is performed emergently and reveals cloudy cerebrospinal fluid with the following values: WBC 1,200/μL (90% neutrophils), protein 185 mg/dL, glucose 18 mg/dL (serum glucose 98 mg/dL), Gram stain shows gram-negative diplococci. She denies recent travel, rash, or sick contacts. Which of the following is the most appropriate initial treatment regimen?