Micro & Immunology · single question
Which bacteria causes ERYSIPELAS (skin infection)?
Show answer and explanation
Correct answer: D. Streptococcus pyogenes (Group A beta-hemolytic Streptococcus)
Erysipelas is a superficial skin infection involving the upper dermis and superficial lymphatics, caused by Streptococcus pyogenes (Group A beta-hemolytic Streptococcus, GAS). It presents as a well-demarcated, raised, bright-red 'butterfly rash' on the face with clear borders and systemic features (fever, chills). Treatment: penicillin G or amoxicillin.
- A. CORRECT. Streptococcus pyogenes (Group A beta-hemolytic Strep) is the classic cause of erysipelas — the sharply demarcated red facial rash with lymphatic involvement.
- B. Incorrect. S. aureus causes cellulitis (deeper dermis/subcutaneous), impetigo, and folliculitis — but NOT typically the superficial, sharply demarcated erysipelas.
- C. Incorrect. S. viridans is an alpha-hemolytic strep associated with subacute bacterial endocarditis — not erysipelas.
- D. Incorrect. P. aeruginosa is an opportunistic Gram-negative rod associated with hospital-acquired infections, burns, and cystic fibrosis — not erysipelas.
Practice Micro & Immunology questions Micro & Immunology study notes