Induction and Evasion of Host Defenses by Type 1-Piliated Uropathogenic <i>Escherichia coli</i>

TLDR

Type 1 pili are filamentous adhesive organelles present in virtually all uropathogenic *Escherichia coli* strains. Electron microscopy showed that type 1 pili bind uroplakins on bladder cells, are shortened to promote intimate contact, trigger rapid apoptosis‑like exfoliation of epithelial cells, and enable bacteria to invade the epithelium to evade clearance.

Abstract

Virtually all uropathogenic strains of Escherichia coli encode filamentous surface adhesive organelles called type 1 pili. High-resolution electron microscopy of infected mouse bladders revealed that type 1 pilus tips interacted directly with the lumenal surface of the bladder, which is embedded with hexagonal arrays of integral membrane glycoproteins known as uroplakins. Attached pili were shortened and facilitated intimate contact of the bacteria with the uroplakin-coated host cells. Bacterial attachment resulted in exfoliation of host bladder epithelial cells as part of an innate host defense system. Exfoliation occurred through a rapid apoptosis-like mechanism involving caspase activation and host DNA fragmentation. Bacteria resisted clearance in the face of host defenses within the bladder by invading into the epithelium.