A 6-year-old child presents with acute pharyngitis and tender cervical lymphadenitis. A throat swab culture shows beta-hemolytic colonies. A bacitracin disc placed on the plate shows a zone of inhibition. Which M protein serotype is most associated with this organism causing pharyngitis?
- A M protein type 12
- B M protein type 1 and 3 ✓
- C M protein type 49
- D M protein type 60
Correct answer: B. M protein type 1 and 3
Explanation
Bacitracin sensitivity identifies Group B Streptococcus (Streptococcus pyogenes). M protein types 1 and 3 are most commonly associated with pharyngitis. M protein type 12 is associated with post-streptococcal glomerulonephritis. M protein type 49 is associated with pyoderma and subsequent glomerulonephritis.
Reference: Ananthanarayan and Panicker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.