CHICAGO, March 17 (Xinhua) -- Researchers at Washington University School of Medicine in St. Louis and Mayo Clinic have found, in newborn mice, that a molecule called epidermal growth factor in breast milk activates receptors on intestinal cells to keep dangerous gut bacteria from migrating into the bloodstream, where such microbes can prompt sepsis.

In the study, the researchers gave newborn mice a solution containing Escherichia coli bacteria isolated from the bloodstream of a late-onset sepsis patient shortly after birth. The mouse pups then were nursed either by their own mother or another mother who had given birth to pups at an earlier time, resulting in her breast milk containing lower amounts of epidermal growth factor.

The mice that developed blood infections were those nursed by females that had been lactating for longer periods of time and, therefore, had lower levels of epidermal growth factor in their milk.

"One of the big implications is not only the necessity of using breast milk to feed preemies whenever possible," said Kathryn A. Knoop, an assistant professor of immunology at Mayo Clinic and the study's first author, "but milk with higher concentrations of epidermal growth factor."

Newberry said it may be possible to add epidermal growth factor to donor breast milk or formula that has lower amounts of the important substance.

"Frequently, donor milk is donated by women near the end of their lactation," he said. "But that milk may not be maximally beneficial to premature babies. We think it may be possible to increase the concentration of epidermal growth factor in the milk that lacks adequate amounts so that we can give that fortified milk to premature infants."

Unlike antibiotics that tend to kill bacteria indiscriminately, breast milk containing higher amounts of epidermal growth factor would not kill harmful or beneficial bacteria in the gut, but might keep such bacteria out of the bloodstream.

"This probably is not a strategy that we would use to treat an infection," said co-investigator Phillip I. Tarr, a professor of pediatrics and director of the Pediatric Division of Gastroenterology, Hepatology and Nutrition at the university. "But it may well be useful in the near future to prevent potentially deadly infections."

Late-onset sepsis strikes at least 72 hours after a baby is born and up to 60 days after birth and accounts for 26 percent of all deaths in infants born prematurely. About 10 percent of infants born preterm experience late-onset sepsis, and 30 percent to 50 percent of those who develop the infections die.

The findings were published Monday in the Proceedings of the National Academy of Sciences.