23-year-old man is admitted to the Emergency Department with an

evolving purpurie rash, pyrexia and confusion. The resident had given

him intramuscular benzyl-penicillin immediately. Which one of the

following investigations is MOST likely to reveal the diagnosis?

A. Urinary antigen

B. Blood PCR for meningococcus

C. Blood culture

20 D. CT head

E. Lumbar puncture