Chapter 9 - Uropathogenic Escherichia coli

Abstract

Uropathogenic E. coli (UPEC) are a genotypically diverse subset of extraintestinal pathogenic E. coli that cause urinary tract infections. UPEC have evolved from commensal E. coli by acquisition of virulence factors through horizontal gene transfer. Through reductive evolution, asymptomatic bacteriuria strains have evolved from UPEC to live a commensal-like lifestyle in the urinary tract. UPEC, unlike diarrheagenic E. coli, have no core set of virulence factors; instead, this pathotype uses flagella to ascend the urinary tract, and a variety of adhesins, iron acquisition systems, and toxins to colonize the bladder and kidneys. While distinct virulence factors have been associated with uropathogenicity, there is also functional redundancy. Some virulence factor genes such as those encoding type 1 and P fimbriae undergo phase variation, leading to a bacterial population with mixed expression. Strain variation resulting from both a heterogeneous set of virulence factors and phase variation leads to a phenotypic diversity that complicates vaccine development against UPEC and likely allows for recurrent infections.