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Pitting Germ Against Germ Prevents Infections

SAN FRANCISCO--Tell a kid to smear an open sore with germs, and she'll think you're teasing. But some scientists say this approach might keep the pus away. Applying a harmless bacterium or its products to surgical implants thwarts infections, researchers reported here 12 December at the American Society for Cell Biology meeting. This is the first time anyone's used friendly bacteria in such a way, other researchers say, and the technique might help prevent serious wound infections in people someday.

Infections of Staphylococcus aureus--better known as "staph"--can cause complications and even death in surgical patients. The bug has become even more threatening in recent years because many strains have developed resistance to antibiotics.

But conventional antibiotics might not be the only ways to squelch staph. A team of researchers led by biochemist Jeffrey Howard and microbiologist Gregor Reid of the University of Western Ontario knew from earlier research that a protein from Lactobacillus--a microbe that lives peacefully within humans--keeps staph from binding to Teflon and glass. This protein also binds to a molecule that staph sticks to when it invades humans. The researchers reasoned that the Lactobacillus protein might successfully compete with staph in animal tissue as well.

To find out, the team placed a small piece of silicone under the skin of rats to mimic a surgical implant, then added S. aureus to the wound. As expected, serious infections developed. When the researchers added staph plus live Lactobacillus, however, none of the nine animals got an infection, compared to five of the nine animals in the control group. The secreted protein also protected the animals from infection, although somewhat more modestly.

The idea of using Lactobacillus or its products to prevent staph infections "is exciting and very sound," says microbiologist William Costerton of Montana State University in Bozeman. Although people have pitted one bacterium against another for medical purposes before--particularly in the intestinal and genitourinary tracts--applying the strategy to wounds is "unique," he says. "There are a lot of bacteria around, and you can think of a wound as a sort of ecological battlefield"--one in which the good germs can beat the bad.

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