Bacteria: Structure and Pathogenesis · USMLE Step 1

What is the primary role of lipopolysaccharide (LPS) in Gram-negative bacteria in pathogenesis?

  1. Mediating adherence to host cells
  2. Endotoxin causing inflammation
  3. Catalyzing peptidoglycan cross-linking
  4. Initiating bacterial DNA replication
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Correct answer: Endotoxin causing inflammation

LPS (especially the lipid A portion) acts as an endotoxin that can trigger strong inflammatory responses and septic shock when released. It is a major virulence factor in Gram-negative infections.

Difficulty: Medium Question 7 of 17

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