Two Arizona State University professors are trying to dig up new medical cures, studying the use of clay to combat some of the planet's deadliest bacterial infections.
The researchers, geochemist Lynda Williams and microbiologist Shelley Haydel, already have demonstrated that certain clays are able to wipe out microbes responsible for MRSA (methicillin-resistant Staphylococcus aureus), as well as intestinal bugs such as E. coli and salmonella. But they remain stumped as to how it works.
"We know they kill bacteria, but we don't know why," Williams said. "The 'eureka' moment - we haven't had that yet."
On Sunday, Haydel presented the team's latest findings at a meeting of the American Chemical Society in New Orleans. No clinical studies have been conducted with lab animals or human patients, but the researchers are seeking new grant funding and hope to begin studies on mice.
The goal is to find a cheap, accessible cure for deadly infections worldwide, Williams said. "That would make me happiest. . . . And I'm sure pharmaceutical companies would like to know the recipe."
Williams said she became interested in the medicinal potential of clay five years ago after learning about Line Brunet de Courssou, a French diplomat's wife then working in the Ivory Coast with victims of Buruli ulcers, caused by a flesh-eating mycobacterium. Photographs documented that daily poultices of green volcanic mud destroyed the microbes and enhanced healing for about 100 patients.
"It killed the ulcer. The only other treatment was excision (by surgery)," Williams said. "I was fascinated by the story."
Williams was not surprised that clay can be beneficial. Mud baths are popular spa attractions, and field geologists often treat wounds with clay because it stems bleeding and absorbs toxins. But she found no scientific studies about clay's antiseptic properties.
Two years ago, Williams and Haydel teamed up, using a $440,000 grant from the National Institutes of Health to analyze chemicals with an electron microscope and conduct lab tests on bacteria.
They focused on volcanic soils known as bentonite, featuring layered silicate sheets. Clay is essentially a type of dirt formed of crystalline particles that measure 2 microns or less in diameter. The expandable structure absorbs water along with elements such as aluminum, iron and magnesium. As a result, every vein of clay features unique compounds and acidity levels.
So far, the scientists have checked more than 30 different clays from around the world, placing extracts in petri dishes with MRSA bacteria and other public-health threats.
Haydel recalls her shock when two additional clay samples, from Nevada and Oregon, annihilated pathogens. "I thought, 'We might have something here. We need to find out how it's killing them.' "
That question remains unanswered and puzzling. The antiseptic clays are not uniform in chemistry or color. The microbes they kill differ in structure and genetics. So the antibacterial recipe remains a mystery.
Williams and Haydel admit to initial misgivings about their study because clay's medicinal power is so tangled in folk remedies and fraud.
Historical references date to the Greeks, and to a biblical account of Christ mixing spit and clay to cure a blind man. The substance was used to treat soldiers' wounds in World War I. It has been consumed as a palliative by indigenous groups and by pregnant women in Appalachia.
Even today, a Google search pulls up dubious claims about clay as a remedy for everything from acne to autism to indigestion.
Williams held up a bottle of gray-colored water and gunk that the researchers acquired. Known as "Black Manna," the product had no impact on microbes in lab tests, she said, but the label claims it "increases overall sense of well-being."
"Nobody's ever shown that the majority of what's said out there is scientifically accurate," Haydel said.
She and Williams set out to change that, at least in terms of killing bacteria. After reporting initial findings to the Geological Society of America last year, they began receiving clays and testimonials from around the world. One man claimed to be selling Dead Sea mud that actually was Illinois dirt laced with cornstarch, Williams said. Another clay with supposed healing powers contained toxic concentrations of arsenic at 500 times the level approved by the Environmental Protection Agency.
"Until we understand the chemistry, I have to warn people not to be eating clay," Williams said.
To that end, the researchers are seeking a five-year, $1.8 million grant for further study. Haydel said she's already applied clay to a cut she had. "It was actually soothing."
But the active compounds have to be isolated and clinical studies must be done before human treatment is even considered.
"We've got a lot of ideas," Haydel said, "but we're years away from ever internalizing this and making sure it's safe."
Reach the reporter at dennis
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