This 19-year old student was in his usual state of health until the evening prior to admission, when he went to bed with a headache. He told his mother that he felt feverish, and on the following morning his mother found him in bed, moaning and lethargic. He was brought to the emergency room, where he appeared toxic and drowsy but oriented. His temperature 40'C, his heart rate was 126/min, and his blood pressure was 100/60 mm Hg. His neck was supple. He had an impressive purpuric rash, not blanching, most prominent on the trunk, legs and wrists. His white blood cell count was 26,000/ul with 25% band forms. The platelet count was 80,000/ul.

Blood cultures were obtained, a lumbar puncture was performed, and the patient was begun on intravenous ceftriaxone. Cerebrospinal fluid (CSF) glucose, protein, and white blood cell count were normal, and CSF bacterial culture was negative. Blood cultures grew a Gram Negative diplococci.

1. What is the organism causing his illness? Is the finding of a normal CSF profile without evidence of meningitis commonly observed in infection with this organism? Explain.

2. Is this organism ever part of the normal oropharyngeal microbiota? Explain.

3. How is this disease spread? How can infection be prevented?

4. What is a purpuric rash, and which virulence factor plays a central role responsible for its appearance?