E. coli poses significant public health threat to seniors in the U.S.

A new study finds that E. coli bacteremia - a potentially life-threatening bloodstream infection caused by a common bacteria also associated with less dangerous urinary tract infections - poses a significant public health threat in the United States, especially among seniors.

The study, published by Group Health researchers in the May issue of the Journal of Infectious Diseases, finds E. coli bacteremia may affect as many as 53,000 non-institutionalized people, aged 65 and older, each year. It also suggests that a vaccine or other preventive intervention, targeted at high-risk groups, could have an important, positive impact on public health.

The bacterium Escherichia coli (E. coli), which grows naturally in the human digestive tract, is a leading cause of urinary tract infections. Medical researchers have long known that E. coli is also a cause of bloodstream infection. But until this study, the number of non-institutionalized seniors affected by E. coli bacteremia has not been clear.

"E. coli is a less serious problem in the urinary tract, but if it spreads to the bloodstream it causes bacteremia, which can lead to a dangerous drop in blood pressure called septic shock," explained Lisa Jackson, MD, MPH, a senior investigator at Group Health's Center for Health Studies and the lead author of the study. "Bacteremia is associated with a death rate of about 10 percent," Jackson added.

While there is a vaccine to protect seniors from pneumococcal bacteremia, which starts in the lungs, there is no similar vaccine to protect against E. coli bacteremia. "Our study finds E. coli bacteremia three times more common than the pneumococcal infection," said Jackson. "That suggests that development of a vaccine could save many lives."

While studies are underway at other institutions on a vaccine that would prevent bacteria from taking hold in the urinary tract, Jackson said she is not aware of any work currently underway to develop a vaccine specifically to prevent E. coli bacteremia.

Jackson's study, conducted among 46,000 Group Health members, also identified risk factors for E. coli bacteremia. In men, they include urinary catheterization and incontinence. In women, risk factors are linked to incontinence, congestive heart failure, and coronary artery disease.

Certain health behaviors can help prevent urinary tract infections, and, by association, may also help reduce the risk of bacteremia. Information on these preventive measures is available online from the National Institutes of Health.