Watch out hand sanitizer. Clay kills bacteria too.

Photomicrograph of clay. Lynda Williams/Arizona State University

Friday, November 2nd, 2007--

Researchers report that clay--straight out of the ground--can kill certain bacteria as effectively as antibiotics. One type of french green clay was shown to wipe out Escherichia coli (the cause of urinary tract infections), Salmonella typhimurium (associated with food born illness), and Pseudomonas aeruginosa (a problem for burn patients). It also did significant damage to the antibiotic-resistant strain of E. coli and inhibited the growth of Methicillin-resistant Staphylococcus aureus (MRSA), says Shelley Haydel, a microbiologist at Arizona State University in Tempe.

"We don't at this point in time know how the clay is actually affecting the bacteria. We just know that for some of the bacteria, it is killing it significantly," says Haydel.

The inspiration for the research can be traced back to the late Line Brunet de Courssou--a French humanitarian, who claimed she had success using specific types of french green clays to heal Buruli ulcers--a flesh-eating disease found on the Ivory Coast, Africa, among other places. But Brunet de Courssou was not a scientist and so her son queried the Clay Minerals Society list serve to see if any researchers would look into his mother's findings, the researchers say.

Enter Lynda Williams--a geochemist at Arizona State University. Williams, who responded to the query, and Haydel are now looking at whether the clays are effective and if so, how they work. They presented their initial findings this week at the 2007 meeting of the Geological Society of America in Denver.

Williams says that one of the clays Brunet de Courssou championed does in fact kill bacteria in the lab, while another clay Brunet de Courssou used actually promotes bacterial growth. They found "two opposite effects from clays that are chemically similar, minerologically identical," says Williams. The clays differ in their trace elements.

The clay doesn't appear to be physically attacking the bacteria. "There's no evidence of the clay wrapping around the bacteria and suffocating it. And there is no evidence of the clay particles penetrating the cell wall or ripping apart the cell wall at all," says Williams.

The alternative explanation is that the clay is killing with chemicals. "We think it is something that is coming off of the clay and transfering to the bacteria," says Williams. Trace elements in the clay--like arsenic and silver--could kill bacteria, but no single element is present in particularly high levels. "We look at the levels of those elements in the solutions, and none of the concentrations are high enough to be inhibitory to bacteria alone," says Haydel. This suggests that the mix of chemicals may be creating an environment that is toxic to the bacteria, perhaps due to pH or the amount of oxygen in the solution, Williams says.

Should big pharma be worried? Haydel doesn't think so. "This is an alternative approach to medicine. Are we ready as a mainstream population to accept that? The answer probably is no."

--Flora Lichtman

Sources

Lynda Williams
Associate Research Professor School of Earth and Space Exploration Arizona State University Tempe, Arizona 85287-1404

Shelley Haydel
Assistant Professor in the School of Life Sciences Researcher in the Center for Infectious Diseases and Vaccinology Biodesign Institute Arizona State University Tempe, AZ