This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacterial infections, Subject name: Dental
[{'content': 'Erysipelas is a skin infection often caused by \nSelect and explain. \nA. Erysipelothrix rhusiopathiae, B. Streptococcus pyogenes, C. Pseudomonas aeruginosa, D. Trichophyton rubrum', 'role': 'user'}, {'content': "Answer: B \nExplanation: STREPTOCOCCAL INFECTIONS * Gram-positive bacteria arranged in chains or pairs . * Not pa of normal cutaneous flora (but resident of aerodigestive tract and vagina). * Classification two methods: a) Ability to induce hemolysis (a, b, g) and/or b) Lancefield groups (A-D, G) based on characteristic polysaccharide cell wall * Of note, group A b-hemolytic streptococci (S. pyogenes, GAS) most pathogenic. Erysipelas (St. Anthony's Fire):- * Superficial type of cellulitis with significant dermal lymphatic involve-ment; typically due to GAS. * Presents as a well-defined, bright red indurated plaque with sharp, raised borders commonly on the face or legs, +- constitutional symptoms. Treatment of choice:- Penicillin (PCN) (if PCN allergic can use macrolide). Ref:- Sima Jain; pg num:-206", 'role': 'assistant'}]