Question:medium
Which structural component of Group A Streptococcus enables its attachment to pharyngeal epithelium by binding to fibronectin?
Which structural component of Group A Streptococcus enables its attachment to pharyngeal epithelium by binding to fibronectin?
Show Hint
Group A Streptococcus attaches to pharyngeal epithelium using lipoteichoic acid binding to fibronectin.
Updated On: May 14, 2026
- Lipoprotein
- Lipoteichoic acid
- Capsule
- Flagella
Show Solution
The Correct Option is B
Solution and Explanation
Step 1: Understanding the Question:
We need to identify the adhesin of Group A Streptococcus (Streptococcus pyogenes) that mediates the initial attachment to host cells via fibronectin.
Step 2: Detailed Explanation:
Adhesion Mechanism: The pathogenesis of S. pyogenes infection begins with colonization of the pharynx or skin. This requires multiple surface components that act as adhesins.
Lipoteichoic Acid (LTA): LTA is a major component of the cell wall of Gram-positive bacteria. In Group A Streptococcus, LTA is part of the pili and is associated with the M protein on the cell surface. LTA binds specifically to fibronectin, which is a glycoprotein present on the surface of host epithelial cells. This interaction is critical for the initial docking of the bacteria.
M Protein and Protein F: Other components also play a role. Protein F (Fibronectin-binding protein) is also a major adhesin. However, among the provided choices, LTA is the classic recognized component for this specific binding.
Why not others? The capsule (Option C) is made of hyaluronic acid and is primarily an anti-phagocytic factor rather than an adhesin. Flagella (Option D) are not present in Streptococci, which are non-motile.
Step 3: Final Answer:
Lipoteichoic acid (LTA) is the structural component that binds to fibronectin for pharyngeal attachment.
We need to identify the adhesin of Group A Streptococcus (Streptococcus pyogenes) that mediates the initial attachment to host cells via fibronectin.
Step 2: Detailed Explanation:
Adhesion Mechanism: The pathogenesis of S. pyogenes infection begins with colonization of the pharynx or skin. This requires multiple surface components that act as adhesins.
Lipoteichoic Acid (LTA): LTA is a major component of the cell wall of Gram-positive bacteria. In Group A Streptococcus, LTA is part of the pili and is associated with the M protein on the cell surface. LTA binds specifically to fibronectin, which is a glycoprotein present on the surface of host epithelial cells. This interaction is critical for the initial docking of the bacteria.
M Protein and Protein F: Other components also play a role. Protein F (Fibronectin-binding protein) is also a major adhesin. However, among the provided choices, LTA is the classic recognized component for this specific binding.
Why not others? The capsule (Option C) is made of hyaluronic acid and is primarily an anti-phagocytic factor rather than an adhesin. Flagella (Option D) are not present in Streptococci, which are non-motile.
Step 3: Final Answer:
Lipoteichoic acid (LTA) is the structural component that binds to fibronectin for pharyngeal attachment.
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