Dynamic interactions between host and pathogen during acute urinary tract infections

Urinary tract infections (UTls) have traditionally been viewed as acute and often self-limiting infections caused predominantly by noninvasive Escheri chia coli, However, this concept has been challenged by recent findings dem onstrating that an acute bladder infection results from a complex series of host-pathogen interactions that can lead to bacterial invasion and persist ence and that ultimately can determine the course of the infectious disease . The ability of E. coli to gain a foothold in the bladder is greatly facil itated by type pilus-mediated attachment to and invasion of bladder epithel ial cells. Invasion allows uropathogenic strains of E. coli to exploit the intracellular environment by replicating within these epithelial cells whil e evading a multitude of host defenses. An intracellular location also prov ides them a safe haven from many common antibiotic therapies. However, atta chment and invasion also activates a cascade of innate host defenses, leadi ng to the death and exfoliation of bladder cells and the production of infl ammatory mediators. The ability of uropathogenic E. coli to flux out of cel ls and colonize surrounding cells provides them a mechanism to subvert thes e defense mechanisms and persist in the bladder epithelium for weeks follow ing the acute infection. The persistence of E. coli in bladder tissue may b e relevant to more chronic diseases of the urinary tract such as recurrent UTls and interstitial cystitis. (C) 2001, Elsevier Science Inc.