Women's Health: Bacteria may bounce back to trigger repeat urinary tract infections

Researchers believe they've discovered why some urinary tract infections keep coming back after apparently successful antibiotic treatment: A small percentage of bacterial cells go into a dormant state and can't be detected by standard tests.

About one-quarter of women who appear to be cured of their urinary tract infection develop another one within six months. Most of the infections are caused by E. coli bacteria, which are thought to be completely killed by antibiotic treatment. But three doctoral students at the University of North Carolina in Charlotte have shown that commonly used antibiotics can induce some bacteria to enter a dormant state.

These dormant bacteria are not detected by standard tests, but are still capable of multiplying, according to Whitney Gray, Shereef Soliman and Hadley Hartwell, who are students of Todd Steck, an associate professor of biology.

In a laboratory study, the students used two antibiotics to kill E. coli bacteria. But after 42 days, between 0.06 per cent and 5.7 per cent of the starting cell population remained viable, as determined by two tests.

"These results suggest that E. coli cells can escape antibiotic killing ... and serve as the source of subsequent infections," the group concludes.