What is the role of intimin in EPEC pathogenesis?

• A. It acts as a toxin damaging host cells.
• B. It mediates attachment to enterocytes leading to attaching and effacing lesions.
• C. It helps bacteria invade and replicate inside macrophages.
• D. It forms a capsule to resist phagocytosis.

Answer: (B)

Intimin serves as an outer membrane adhesion protein that drives the direct, intimate attachment of EPEC to intestinal epithelial cells. It doesn’t act as a toxin; instead, it binds to Tir, a receptor inserted into the host cell membrane by the bacteria’s type III secretion system. This interaction anchors the bacteria to the cell surface and triggers rearrangements of the host cytoskeleton, producing the characteristic attaching and effacing lesions with microvilli effacement and pedestal formation under the adherent bacteria. This tight adherence is central to how EPEC causes disease, leading to diarrhea. The other ideas describe toxin activity, intracellular invasion, or capsule-based resistance, which are not the role of intimin.