POSTED 10 APRIL 2008
Say hey for clay!
The battle against infectious disease is stalling. Aided by rapid evolution, bacteria, fungi and other pathogens are finding holes in our immune systems -- and defeating the antibiotics that used to protect us.
Microbiologists have issued an all-points bulletin for new microbe-fighting chemicals, and now we hear about some fascinating editions of the antibiotic-of-the-month club: alligator blood and clay. We'll get to the gators shortly (unless they get to us first!), but clay?
Sure, clay looks humble, but it could contain powerful chemicals that fight deadly, disfiguring infections, including Buruli ulcer and several drug-resistant bacteria. Photo: Arizona State University, John C. Phillips.
Clay, a geologic material with grains no bigger than two microns across, has been used in medicine since Roman times. Some people eat clay directly, others guzzle it in medicines like Kaopectate, which contained clay until quite recently. And spa-goers get smeared with mud or clay to revitalize their skin.
Although some people have claimed that clay can kill harmful microbes, that proposition had almost no scientific backing -- until now. In a report at the April meeting of the American Chemical Society, Arizona State University scientists Shelley Haydel and Lynda Williams reported that two clays, from Nevada and Oregon, can fight or kill some nasty bacteria, including antibiotic-resistant Escherichia coli, Pseudomonas aeruginosa, and methicillin-resistant Staphylococcus aureus (MRSA).
The difficult-to-control MRSA kills, on average, 5,500 people each year in the United States.
Williams and Haydel also found that a third clay, from France, can kill the bacteria that causes Buruli ulcer, and at last we bounce back to the starting point for today's Why File. Buruli ulcer is a nasty skin infection caused by Mycobacterium ulcerans, and it's advancing in Central and West Africa. Although Buruli can be treated in the early stages, antibiotics are less helpful against the later stages, where expensive, disfiguring surgery and skin grafts may be needed. About two-thirds of the patients lucky enough to get surgery are still disabled by the ulcer, according to the World Health Organization (WHO).
If not treated early and properly, Buruli ulcer can cause serious complications, and yet few Africans can afford surgery. Could clay help? Photo: WHO
Grim though it may be, Buruli is a disease of poor people in distant lands, and so it attracted little attention.
An Internet cure?
In 2002, Williams answered an online request from a French man who wanted to get micrographs of some green clay that, he said, had been used by his mother to cure dozens of Buruli ulcers in Ivory Coast. Even though his mother, Line Brunet de Courssou, had photos to back her claims, she was a humanitarian, not a doctor, and the WHO was not impressed enough to fund research on clay.
Williams, an associate research professor who normally concentrates on analyzing clay to improve the odds of drilling for petroleum, agreed to take pictures, thinking, "I would love to know how clay is killing a flesh-eating disease."
Williams teamed up with Haydel, a specialist in tuberculosis, which is caused by a different mycobacterium, and the two began to study clay samples. While Williams focused on structure and composition, Haydel put the clay through standard lab tests used to evaluate antibiotics. She took one clay that Brunet de Courssou used, mixed it with 1,000 parts of water, and found that the solution could kill the bacterium that causes Buruli -- and several other pathogens as well.
The bacteria that causes Buruli ulcer is difficult or impossible to control in its later stages. Many patients, largely children, are disfigured for life, even if they can find and afford surgery and skin grafts. New research shows that a simple clay treatment could do a better job, faster and cheaper? Photo by Paul D. R. Johnson, Courtesy PloS Medicine
Getting a grip on clay
Even at such a dilution, Williams says, the clay "sterilized everything we tested, all these different bacteria, with all these different structures, different metabolic functions, and the clay was killing them all." So how does the clay work? Clay could carry toxic metals that kill the bacteria directly, but that did not seem to be true of the three healing clays, Williams says.
One clue came from structure: all three clays are built of microscopic plates. "This clay has a very large surface area, hundred of square yards per gram, in two silicate sheets that are loosely bound together," Williams says. And so the answer could lie between the sheets (note to self: are we writing science or a romance novel?) "All kinds of elements, which may be toxic to bacteria … can be fixed in the interior," Williams says. When her research group cleaned out the area between the sheets, "the clay no longer killed," she adds.
But there's more. Williams thinks that when it is dissolved in water, the clay holds the water within a certain range of acidity and oxygen content that help murder the bacteria. In other words, the clay serves as a combination delivery truck and treatment boss that can constrain the conditions to those that can waste the bugs.
Not too shabby for microscopic sheets of mineral particles that sandwich whatever fragments of this 'n that happened to accumulate inside the clay.
Smectite clays, like the healing clays being investigated at Arizona State University, have flat plates that can trap a wide range of chemical compounds. These trapped compounds may account for the antibiotic properties of healing clays.
The "but" clause
Every good science story needs some "but" clauses, so here goes:
The first but: Although Williams has more samples of the bactericidal French clay, she has not been able to track down its source. One Internet merchant apparently ordered it from another Internet merchant… .
The second but: Even if one clay is helpful, others may still be harmful: The second clay that Line Brunet de Courssou used to treat Buruli ulcer actually helped the bacteria grow, which proves the folly of placing blind faith in "natural products." Clays can contain worm eggs, spores of pathogenic bacteria, and toxic metals like arsenic or mercury, Williams says. "People like natural cures, but they don’t really seem to understand that just because it's natural does not mean it safe."
Rather than use a natural, and therefore variable, product, Williams hopes to identify the active ingredients in clay and use them as a basis for a drug.
Clay battle continues
Meanwhile, Haydel is concentrating on bacteria that are causing problems in U.S. hospitals. About 30 percent of major burn patients develop infections with pseudomonas, MRSA or E coli, she says. Many of these infections start on the skin, making them an ideal target for a clay-derived treatment. Beyond killing bacteria, clay may also promote healing by serving as a barrier. "We might want to use this like a poultice, that acts as a protectant, almost like a clay Band Aid."
Haydel admits that using clay to kill bacteria has changed her view of traditional medicine. "Validating this in my own lab has given me newfound appreciation for alternative medicine." But that appreciation does not extend to the WHO, whose guidelines on treating Buruli ulcer mention no clay.
Want to tell the WHO about the antibiotics in gator blood?
Megan Anderson, project assistant; Terry Devitt, editor; S.V. Medaris, designer/illustrator; David Tenenbaum, feature writer; Amy Toburen, content development executive
