ASU researchers are proving that clay from the ground can kill even the strongest bacteria, including the flesh-eating "superbug" MRSA.

Though clay has long been used for healing and cosmetic purposes, Lynda Williams of the School of Earth and Space Exploration said the discovery of its ability to kill bacteria, including methycillin resistant Staphylococcus aureus, or MRSA, is new. She and her team presented their findings so far at the American Chemical Society's meeting earlier this month.

"There are people who have used clay for health for years," Williams said, adding that people today swear by ingesting clay to cure strep throat and stomach complaints. "[But] nobody's really realized that it kills bacteria," she said.

Williams began working with one type of healing clay from France in 2002 after learning that a group was using it in Africa to treat skin infections. After hearing about the group's success, she began to analyze the clay to determine its contents and try to figure out why it kills bacteria.

"That could be worth discovering — how nature does it," Williams said.

Since then, Williams and her co-researcher, Shelley Haydel, have found two other anti-bacterial clays from the U.S. The samples vary in shade and texture, and the two are trying to determine what sets them apart from other clays.

Haydel, a microbiologist, said the clay is effective against bacteria with a variety of qualities, including E. coli, salmonella and MRSA, often called a "superbug" because of its resistance to traditional antibiotic treatment.

"We've shown that we can actually kill MRSA," Haydel said. "This could be something that can kill the bacteria when the antibiotics can't."

Haydel said the findings could be especially important for developing countries, where severe skin infections are more common. Because the healing properties of the clay are natural, it could also be a cheaper medicine, she said.

"This is basically Mother Nature at her best," Haydel added.

Though the three varieties of clay have different characteristics, Williams said each type is effective at killing various bacteria.

"So far, it's killed everything that we've tested," Williams said.

This shared bacteria-killing ability is probably because the clays were likely produced under similar circumstances, Williams said.

"We think they're associated with volcanic ash," she said.

How the various elements in the clay interact with each other and bacteria is the key to learning why the clay is anti-bacterial.

"We don't believe it's a physical contact that's causing the bacteria to die," Haydel said. "We believe it's a chemical process."

Senior Amanda Turner has been working on analyzing the minerals in the clay and its chemistry since her freshman year. She wrote in an e-mail that she found it surprising at first that clay could be used for medical purposes.

"People always think of mud/clay as dirty," Turner said. "I thought that, if clays actually killed bacteria, then surely the pharmacy companies should have already known about it. Apparently not."

Reach the reporter at: claudia.koerner@asu.edu.