What makes some clays powerful antimicrobial agents?

Oct 29 2007

What makes some clays such powerful antimicrobial agents capable of killing MRSA and other virulent bacteria?

It's a question that University at Buffalo researchers have been studying for several years.

With funding from the National Institutes of Health-National Center for Complementary and Alternative Medicine, the UB geologists are studying the surface characteristics of a broad range of naturally occurring antimicrobial clays, including some clays from France to determine why they are such effective killers of bacteria.

Researchers from Arizona State University's School of Earth and Space Exploration, to whom the UB researchers are under subcontract on that grant, have recently shown that these French clays can destroy Methicillin-Resistant Staphylococcus Aureus, also called MRSA.

The UB researchers also have modified and patented a type of clay that is highly successful in destroying a range of bacterial agents. It will soon be tested against MRSA.

Some of their results will be presented today at the annual meeting of the Geological Society of America in Denver.

Rossman Giese, Ph.D., professor of geology in UB's College of Arts and Sciences, and Tracy Bank, Ph.D., assistant professor of geology at UB, are using several techniques to study the clays, including atomic force microscopy.

In particular, they study the weak interactions that are responsible for the stickiness of clay particles.

"We look at the attraction or repulsion between natural and modified clays and bacteria," said Giese.

Unlike antibiotics, which are essentially a chemical weapon against bacteria, antimicrobial clays kill through purely physical means, he explained.

"The bacterium has to come into physical contact with the clay in order for something to happen." Giese said.

That contact turns deadly.

"The antimicrobial agents in the clay poke a hole in the cell wall of the bacterium causing the bacterium to leak to death," he explained. "The nice thing about that is that there is no way that the bacterium can evolve to avoid it, so resistance to the antimicrobial clay is unlikely to become a problem."

The clay developed by UB researchers has been very effective in lab testing.

"Our studies show that when we mix a bit of our modified clay at very low levels into sewage sludge that contains all kinds of bacteria, the modified clay kills everything," said Giese. "Nothing will grow in it."

The formulation developed by Giese and colleagues in the department and in the UB School of Medicine and Biomedical Sciences was recently licensed to a Buffalo startup company, called Bioclay, Inc.

The first application for that product is to treat HEPA filters in hospitals with the clay, in order to trap and kill potentially lethal bacteria.

In addition to Bank and Giese, other UB researchers who developed Bioclay are Pat Costanzo, formerly a faculty member in the UB Department of Geology, Paul J. Kostyniak, Ph.D., professor of pharmacology and toxicology and director of the Toxicology Research Center, and Joseph A. Syracuse, research scientist with the same center.

Bank and Giese are also looking at other antimicrobial properties of clays, including a project with researchers at the UB School of Dental Medicine on how decay-causing bacteria may interact with teeth and how the bacteria might be prevented from remaining in contact with teeth.

The University at Buffalo is a premier research-intensive public university, the largest and most comprehensive campus in the State University of New York. UB's more than 28,000 students pursue their academic interests through more than 300 undergraduate, graduate and professional degree programs. Founded in 1846, the University at Buffalo is a member of the Association of American Universities.

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