Why are some women more prone to urinary tract infections?

Millions of young women suffer every year from acute urinary tract infection. For most of these women, treatment with antibiotics takes care of the condition, but approximately 20 to 40 percent of them face a lifelong battle with recurring infections. The incidence also increases with age. An estimated 10 to 15 percent of women over the age of 60 have frequent recurrence of urinary tract infection.

The culprit is no mystery: E. coli. This is not the E. coli most of us associate with fateful selections at the supermarket, however. The strains of E. coli that cause urinary tract infections are actually found naturally in the intestines.

Ann Stapleton Photo by Gavin Sisk

Dr. Ann Stapleton, an assistant professor of medicine in the Division of Allergy and Infectious Diseases, explains that normally, natural defenses keep these E. coli at bay. But certain acquired and intrinsic bacterial and host factors, such as the use of certain contraceptives, allow E. coli to gain the upper hand and migrate from the gut to the urinary tract.

Stapleton investigates why this infection recurs in some women more than others. “In some women, genetic factors play a role in recurrent urinary tract infections,” she said.

E. coli are three times as likely to bind to vaginal cells of women who have had recurring infections than to cells of women who have no history of infection. This avid binding between E. coli and vaginal and other urinary tissue cells makes it harder for the body to flush away the bacteria, which leads to infection, Stapleton said.

In a recent study, Stapleton identified a mechanism that E. coli exploit to achieve this high level of adherence to urinary tissue cells. The bacteria appear to zero in on two carbohydrate receptors on the outside of the cells. These receptors only occur in a certain proportion of women who have specific blood group phenotypes.

“E. coli is highjacking a normal human variant,” Stapleton said. “This is what pathogens do - check the surfaces of surrounding cells and exploit the molecules that are present.”

Stapleton will discuss her research in detail in a Science in Medicine Lecture, titled “Genetic Factors in Susceptibility of Women to Urinary Tract Infection,” on Thursday, April 20, from 12:15 to 1:15 p.m. in room T-625 of the Health Sciences Center.

The finding is likely only one of several factors that make some women more susceptible to urinary track infections, Stapleton added, but it cuts a path for new research. Ultimately, investigators want to be able to inhibit the adherence of E. coli to their target cells, perhaps with a topical drug that can be administered preventively.

Stapleton received an M.D. from Albert Einstein College of Medicine in 1984. She completed a residency in internal medicine at the University of California, San Francisco, in 1987 and a fellowship in infectious diseases at the UW in 1991. She joined the faculty as an acting instructor in 1992. ¶

Will Morton