October 4, 2001
(The Associated Press) - Food contaminated with a strain of drug-resistant E. coli has emerged as a possible new source of urinary tract infections.
E. coli is a normal inhabitant of the digestive tract that can cause both intestinal upsets and urinary infections. But while E. coli from bad food is a frequent cause of diarrhea and other digestive miseries, urinary tract infections were thought until now to result mostly from inadvertent contact with the victim's own feces.
The new research found that a single, genetically identical strain was responsible for outbreaks of urinary tract infections among women in California, Michigan and Minnesota. Because the germs are exactly the same, investigators assume they came from the same source, and the most likely such source is food.
The research, conducted at the University of California at Berkeley, was based on analysis of 302 cases. It was published in Thursday's New England Journal of Medicine.
"We were really, really surprised," said researcher Amee R. Manges at Berkeley. "When we looked at these organisms from these various different women, many of them turned out to be the same. We weren't anticipating that."
Urinary tract infections are common, especially among women, and cause painful and frequent urination. An estimated 90 percent of them are caused by E. coli, which is becoming increasingly immune to the antibiotics used to clear up the infection.
Manges and her colleagues collected urine samples from women treated for infections at Berkeley's health center over a four-month period. They were compared with samples from health centers at the University of Minnesota and the University of Michigan.
The researchers looked specifically at infections caused by E. coli strains resistant to a common antibiotic, trimethoprim-sulfamethoxazole, sold as Bactrim or Septra.
They found the same strain caused 51 percent of the drug-resistant infections at Berkeley, 38 percent in Michigan and 39 percent in Minnesota.
Manges said they also tested healthy people in California and found the strain in both men and women.
"It's an initial step," said Dr. Walter E. Stamm of the University of Washington School of Medicine, who wrote an accompanying editorial. "It will take further studies to look at this clone, see if it's more widespread."
If the strain is eventually traced to one source or a few sources, then steps could be taken to prevent its spread, he said.
The only other known outbreak of urinary infections from a drug-resistant E. coli strain happened in London in the 1980s. The source of that outbreak wasn't found, and Manges said it would be hard to go back and trace the source of the U.S. cases.
She said the next steps include a large study that closely follows lifestyles and eating habits and other tests to try to determine whether the strain is actually spread through food.
"We have the most logical explanation for it, but we need to get more evidence," she said.
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