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  Geotimes - February 2008 - Trends and Innovations

Miracle Muds
Erin Wayman

Mycobacterium tuberculosis
Janice Carr
Mycobacterium tuberculosis, the infectious agent responsible for tuberculosis, is a close relative of the bacteria that cause Buruli ulcers.

Geologists don’t often get to solve medical mysteries. But when two clays appeared to cure disfiguring bacterial ulcers, a geochemist took on the challenge of discovering how these clays work.

Affecting people in the tropics, Buruli ulcers — caused by Mycobacterium ulcerans, a member of the group of bacteria responsible for leprosy and tuberculosis — are a growing concern in a number of areas, especially in West Africa. Common antibiotics can cure the initial stage of the disease: a painless bump on the skin no bigger than a pimple. But by the time the bump grows into an ulcerous lesion — caused by toxins produced by the bacteria that suppress the immune system and destroy tissue including bone — it's too late to halt the damage.

French humanitarian Madame Line Brunet de Courssou, who operated health clinics in the Ivory Coast, believed Buruli ulcers could be cured. Using a combination of two French clays, water and shea butter, Brunet de Courssou discovered she could heal the ulcers. Patients who received the topical clay mixture experienced only mild scarring after recovery rather than the disfigured limbs that afflict most victims of the disease. After more than 50 cases of recovery had been documented, Brunet de Courssou presented her work to a panel of Buruli ulcer experts at the World Health Organization (WHO) in 2002. Although impressed by her case studies, WHO wanted more scientific evidence of the clays’ healing properties before providing Brunet de Courssou with funding to further treat the disease.

Brunet de Courssou did not live long enough to obtain such scientific evidence, but her son Thierry took up the cause after her death. He posted a request for help studying the clays’ properties through the Clay Mineral Society, which geochemist Lynda Williams of Arizona State University in Tempe initially disregarded. “I ignored it the first time around because it wasn’t anything I knew about,” she says. But a second posting by Brunet de Courssou convinced Williams to lend her geological expertise to help figure out how these clays heal lesions.

Lynda Williams demonstrates the application of the topical clay treatment
Arizona State University
Lynda Williams demonstrates the application of the topical clay treatment, as her colleague Shelley Haydel watches.

Williams enlisted the help of Shelley Haydel, a microbiologist at Arizona State University. Researchers typically overlook the potential of inorganic materials in treating bacterial infections, Haydel says, so she was initially skeptical about the clays. She and Williams tested the clays’ killing abilities against different species of five genera of bacteria, including Mycobacterium marinum (a close relative of M. ulcerans) and drug-resistant strains of Staphylococcus aureus, the cause of Staph infections. The first clay either had no effect on the bacteria, or more surprisingly, in some cases, actually promoted bacterial growth. The second clay was a different story: It either completely inhibited bacterial growth, or at the very least, significantly reduced the number of bacterial cells in test cultures. “I didn’t really expect to see it have an effect on so many different pathogens,” Haydel says. The clay is almost like a broad spectrum antibiotic, she says, which is an important finding, given the rise in antibiotic-resistant bacteria.

Haydel and Williams suspect both clays play a role in treating Buruli ulcers. The first clay stimulates the growth of the body’s natural assortment of bacteria, arousing the body’s immune system, which, in order for an ulcer to form, is “tricked” into submission by M. ulcerans. The second clay may then work with the body’s immune system to fight off the bacteria, Williams and Haydel suggested at the annual meeting of the Geological Society of America in Denver last October. Exactly how the second clay works to kill bacteria is something Williams and Haydel are still trying to figure out. “We’re gradually deducing which components kill the bacteria,” Williams says. “It’s not easy to work out.”

Williams and Haydel are working to see how the two clays — iron-rich smectite clays — differ to determine how the antibacterial clay works. The clays are similar in many ways, including their mineralogy, Williams says. And biogeochemist Tracy Bank of the University of Buffalo in New York says their surface properties are also quite similar. She’s been trying to see if the way the clays adhere to surfaces might help explain why one kills bacteria and the other doesn’t. So far, she’s found no major differences in the way they adhere to silica chemicals and has begun to test the clays directly against bacterial cells. Her initial results show there’s no difference in the way bacteria adhere to the clays. “We did expect them to differ,” Bank says. “I have no idea what to expect with these clays.”

Rather than a physical mechanism accounting for the killing abilities of the bactericidal clay, Williams says there may be a chemical mechanism at work. When she removed positively charged molecules from the clay, it lost its antibacterial properties. And the trace chemistry between the two clays differs, which may be dependent upon the waters in which the clays formed, Williams says — in this case, that may be hydrothermal deposits in the Massif Central area of France, although no one knows for sure. The original French suppliers say they don’t remember where the clays came from, she says, making it nearly impossible to study the environment in which they formed or to retrieve more samples.

Since news of these clays first spread among the geological community, however, Williams says she has received lots of different clays from people promoting their putative healing abilities, and a few seem to work. She and Haydel will continue to test these clays along with the few grams left of the original French clays to pinpoint the exact mechanism by which they hinder bacteria. “Our goal right now is to do a little detective work to measure the physical and chemical properties of [these] clays,” she says. She hopes other geologists will join in on the investigation of how minerals can be used to treat diseases, as such study is only in its infancy, she says.

Wayman is a Geotimes staff writer.

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