Bacteriology USMLE Step 1 Practice Question
A 24-year-old woman presents to the emergency department with fever (39.2°C), vomiting, and a diffuse erythematous sunburn-like rash. Vital signs show hypotension (88/56 mmHg), tachycardia (118 bpm), and tachypnea (22 bpm). She started her menstrual period yesterday and left a tampon in place overnight. Laboratory studies reveal thrombocytopenia (platelets 85,000/μL) and elevated creatinine (2.1 mg/dL). She denies vaginal pain. Which of the following best explains the mechanism of the toxin causing her illness?
Answer choices
- ANonspecific activation of T cells by cross linking MHC II and T cell receptorsCorrect answer
- BInactivation of elongation factor 2
- CCleavage of synaptobrevin at peripheral cholinergic terminals
- DInhibition of the 60S ribosomal subunit
- EBlocking release of inhibitory neurotransmitters from Renshaw cells
- FIrreversible ADP-ribosylation of Gs protein activating adenylyl cyclase
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.