Uropathogenic Escherichia coli - Escherichia coli: Pathotypes and Principles of Pathogenesis - page 269

FIGURE 9.1 UPEC encode a variety of virulence factors. Depicted here are the fimbriae, iron
receptors, afimbrial adhesins, flagella, toxins, and immune evasion proteins that have been tested in
the murine model of ascending UTI.
Fimbrial operons can encode regulatory elements themselves that affect
motility and flagellar expression. For example, a regulatory gene associated
with the Sfa II fimbrial operon, sfaX II , when overproduced, reduces the amount
of FliC, corresponding with lower motility. This same protein also negatively
affects type 1 fimbrial expression ( Sjostrom et al., 2009 ). PapX, a protein
encoded by the P fimbrial operon that has 96% amino acid sequence identity
to SfaX, also inhibits flagellar gene expression in UPEC ( Simms and Mobley,
2008b ). Although the mechanisms are unknown, the expression of type 1 and
Yad fimbriae also inhibit flagellar expression ( Lane et al., 2007b ; Simms and
Mobley, 2008a ; Spurbeck et al., 2011 ), demonstrating that production of fim-
briae can have indirect effects on motility.
Adherence
Colonization of the urinary tract is an essential step in the infection process.
Without binding to the host epithelium, bacteria would be washed out of the
urinary tract by the force of urination. UPEC have several different mechanisms
for adherence to the uroepithelium, including: fimbriae, rod-like appendages
that protrude from the bacterial cell surface culminating in a tip adhesin; fibril-
lae, flexible, extended conformations with adhesins present throughout the