🏥 USMLE Exam Prep

A 50-year-old woman presents with a rapidly spreading, fiery-red, tender, and sharply demarcated rash on her lower leg. She also has a fever and chills. There is no central induration or fluctuance. Which organism is the most likely causative agent?

A Staphylococcus aureus
B Streptococcus pyogenes
C Pseudomonas aeruginosa
D Clostridium perfringens

✓ Correct Answer: Option B

The description of a rapidly spreading, fiery-red, tender, and sharply demarcated rash with systemic symptoms is classic for erysipelas, which is typically caused by Streptococcus pyogenes (Group A Streptococcus).

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