April 6 (Bloomberg) -- Mud clay, used as a folk remedy to heal wounds, soothe indigestion and beautify the complexion, may help doctors fight drug-resistant infections.

In tests of more than 30 clay samples from around the world, researchers found clays from Oregon and Nevada that killed almost all the cells of methicillin-resistant Staphylococcus auereus, a staph infection that can be fatal, according to Arizona State University researchers. The results are being presented today at the American Chemical Society meeting in New Orleans.

While clay today is mostly associated with the mud baths of health spas, people have used it for thousands of years to treat ailments, by eating it or applying it to the skin. If the study findings hold up in human tests, doctors may have new ways to combat infections, the researchers said. The study, funded by the National Institutes of Health, is the first to look at the antibacterial activity of natural clay.

``Since people existed, they have used clays for medicinal purposes,'' said Lynda Williams, a research professor at Arizona State University, in Tempe, in an telephone interview on April 2. ``If we can understand its antibacterial mechanism, then I expect clays will be more prevalent in people's lives.''

The Oregon and Nevada samples also killed almost all cells of E. coli, which causes food poisoning, and destroyed pseudomonas aeruginosa, which causes urinary tract and gastrointestinal infections, as well as deadly infections in people hospitalized with cancer and burns.

A French clay was also effective against MRSA, pseudomonas aeruginosa and E. coli, said researcher Shelley Haydel, an assistant professor of life sciences at Arizona State.

Clay for MRSA

More than 94,000 invasive MRSA infections occurred in the U.S. in 2005, resulting in 18,650 deaths, according to the latest estimates by the U.S. Centers for Disease Control and Prevention. Healing clay might be turned into rub-on creams or ointments to keep MRSA infections from spreading, researchers said.

The scientists theorize that chemicals in the clay may kill bacteria by poking holes in the cells.

``We believe right now it's the chemistries of the clays themselves,'' Haydel said in a telephone interview on April 2. ``We don't have a definitive answer.''

The researchers are planning to study the clay as a topical remedy for wound infections. Until those tests are done, people should be cautious because natural clay also contains toxic minerals such as mercury and arsenic, Williams said.

Whether doctors will embrace clay as a treatment for infections remains to be seen, the researchers said.

``This is a natural, alternative type of treatment approach,'' Haydel said. ``I don't know how traditional medicine will respond to that.''

To contact the reporter on this story: Nicole Ostrow in New York at nostrow1@bloomberg.net.