USMLE Step 1 Practice Test 9

A 19-year-old college student who lives in a dormitory is brought to the emergency department 8 hours after the onset of fever, headache, and vomiting. Temperature is 39.8°C (103.6°F), pulse is 132/min, respirations are 26/min, and blood pressure is 78/40 mm Hg. He is lethargic, and his neck is stiff. Nonblanching purpuric lesions are present over the trunk and lower extremities. Platelet count is 42,000/mm³, and prothrombin time is prolonged. Results of lumbar puncture are shown. A Gram stain of the cerebrospinal fluid shows gram-negative diplococci. Which of the following bacterial components is most directly responsible for this patient's hypotension and purpura?