A 15 year old boy presents to you with history of fever, altered sensorium and purpuric rash for two days. On examination, the patient is found stuporous. He has a BP of 90/60 mmHg and extensive palpable purpura over the legs. Which of he following would be the most appropriate initial choice of antibiotic
Vancomycin
Pencilline G
Ciprofloxacin
Gentamicin