Antimicrobials and Resistance · USMLE Step 1

A woman develops a rash after taking ampicillin for a sore throat. She is later diagnosed with mononucleosis. What explains the rash?

  1. Allergic reaction to β-lactam
  2. EBV-associated immune response
  3. Cross-reactivity with cephalosporins
  4. Drug-induced lupus
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Correct answer: EBV-associated immune response

Ampicillin causes a characteristic rash in patients with EBV mononucleosis, not a true allergy.

Difficulty: Medium Question 19 of 20

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