Enteropathogenic Escherichia coli: a pathogen that inserts its own receptor into host cells

Enteropathogenic Escherichia coli (EPEC) is a major cause of infant diarrhe a, killing hundreds of thousands of children per year worldwide. Intimate a ttachment to the host cell leading to the formation of actin-rich pedestals beneath the adhering bacteria is an essential feature of EPEC pathogenesis . EPEC attaches to host cells via the outer membrane adhesin, intimin. It w as recently shown that EPEC inserts its own receptor for intimate adherence , Tir (translocated intimin receptor) into the host cell membrane. The focu s of this review is on the discovery and characterization of this novel rec eptor, and our current understanding of its role in pedestal formation. Gra m-negative bacterial secretion systems, including type III secretion system s, are reviewed and discussed in the context of Tir delivery into the host cell membrane. The relationship and relevance of in vitro models compared t o the actual in vivo situation is essential to understanding disease. We ha ve critically reviewed the use of animal models in studying EPEC infection. Elucidating the function of Tir will contribute to our understanding of ho w EPEC mediates disease.