Significance of uropathogenic strains of Escherichia coli (UPEC) in the pathogenesis of urinary tract infections

Urinary tract infections (UTIs) are one of the most widespread infections, particularly among women (40-50%) as well as newborns, infants and elderly persons. In addition, recurrent episodes of UTIs are common and frequently become chronic. Escherichia coli is the most common cause of UTIs, bothcommunity- and hospital-acquired, followed by other Enterobacteriaceae (Proteus spp., Klebsiella spp.), Pseudomonas spp. and Gram-positive cocci. The majority of UTIs are caused by uropathogenic E. coli (UPEC) characterized by the presence of various adhesive fimbriae (pili) e.g., type 1 or P, S and Afa/Dr fimbriae, the crucial virulence factors for their pathogenic capabilities. For example, type 1 fimbriae are common among cystitis-associated UPEC, P fimbriae are characteristic adhesins in E. coli pyelonephritis, and Dr fimbriae UPEC strains are frequently isolated (40%) from pregnancy-associated pyelonephritis cases. In consequence, Dr+ E. coli may contribute to serious pregnancy complications, including premature births or damage of the fetus. Therefore, the more extensive knowledge about mechanisms of pathogenesis of UPEC strains may facilitate development of novel diagnostic methods and might prove essential for better risk assessment for patients with UTIs.