Biopsy of intestinal epithelium in an infant with persistent diarrhoea shows cup-like destruction of microvilli with bacteria sitting on raised pedestals of actin. This attaching and effacing lesion of enteropathogenic E. coli (EPEC) is produced when the bacterial outer membrane protein intimin binds to which host-inserted receptor?
- A Bundle-forming pilus anchored on the epithelial surface
- B Tir, translocated into the host cell by a type III secretion system ✓
- C Gb3 glycosphingolipid on the brush border
- D Integrin alpha 5 beta 1 on the basolateral membrane
Correct answer: B. Tir, translocated into the host cell by a type III secretion system
Explanation
EPEC injects its own receptor, Tir (translocated intimin receptor), into the enterocyte through a type III secretion system. Tir is then phosphorylated and presented on the surface where intimin binds it, triggering actin polymerisation and pedestal formation with effacement of microvilli. Bundle-forming pilus mediates initial loose adherence only, not the lesion itself. Gb3 is the Shiga toxin receptor and integrins are targets of Yersinia invasin.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.