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The epidemiology of urinary tract infection
Betsy Foxman
Abstract | Urinary tract infections (UTIs) are among the most common bacterial infections acquired in the community and in hospitals. In individuals without anatomical or functional abnormalities, UTIs are generally self limiting, but have a propensity to recur. Uropathogens have specialized characteristics, such as the production of adhesins, siderophores and toxins that enable them to colonize and invade the urinary tract, and are transmitted between individuals both through person-to-person contact and possibly via food or water. Although generally self limiting, treatment of UTIs with antibiotics leads to a more rapid resolution of symptoms and is more likely to clear bacteriuria, but also selects for resistant uropathogens and commensal bacteria and adversely affects the gut and vaginal microbiota. As uropathogens are increasingly becoming resistant to currently available antibiotics, it may be time to explore alternative strategies for managing UTI.
Foxman, B. Nat. Rev. Urol. 7, 653660 (2010); http://www.nature.com/doifinder/10.1038/nrurol.2010.190
Web End =doi:10.1038/nrurol.2010.190
Introduction
The urethra is a portal for the exit of urine, but also allows the entry of microbes, including pathogens, into the urinary tract. Bacteria live around the urethral opening in both men and women and routinely colonize urine in the urethra, but are washed out during micturition. The shorter distance to the bladder in women makes it possible for bacterial colonizers to reach the bladder more easily before they are removed by micturi tion. In addition, the urethral opening in women is proxi mate to the vaginal cavity and rectum, which harbor large bacterial communities. Urogenital manipulations associ ated with activities of daily living and medical interventions facilitate the movement of bacteria from the vaginal cavity, rectal opening and periurethal area into the urethra; however, even if bacteria reach the bladder and multiply to significant numbers, only rarely does bacterial coloniza tion result in symptoms. Given human anatomy, it is not surprising that urinary tract infections (UTIs) are among the most common bacterial infections; indeed, we should perhaps be surprised that, given the constant assault on our urinary system by microbes, UTIs are not more common.
Both host and bacterial factors influence the probability that asymptomatic colonization resolves spontaneously or progresses to symptomatic infection (Table 1). Host factors include the presence of anatomical or...