A laboratory uses Staphylococcus aureus Cowan I strain to detect IgG-coated bacteria in a diagnostic assay. Which surface protein of S. aureus binds to the Fc region of IgG, leaving the Fab region free to agglutinate?
- A Clumping factor
- B Teichoic acid
- C Protein A ✓
- D Fibronectin-binding protein
Correct answer: C. Protein A
Explanation
Protein A is a surface protein of S. aureus that binds the Fc portion of IgG. This orients the Fab region outward, allowing the bacteria to agglutinate in the presence of specific antigens, a principle used in coagglutination tests. Clumping factor binds fibrinogen and causes direct clumping. Teichoic acid mediates adherence to nasal epithelium.
Reference: Ananthanarayan and Panicker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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