Wayne Seidl on sat 4 nov 06
This was on another list. Thought we might be interested since we all work
with clay .
Best,
Wayne Seidl
>http://www.scienceagogo.com/news/20061001221856data_trunc_sys.shtml
2 November 2006
Clays Exhibit Novel Antibacterial Properties
Beauty treatments that use clay aren't new, but
clay-based medicinal treatments are. And if Arizona
State University's (ASU) Lynda Williams and Shelley
Haydel's research pans out, then clay might one day
become an antibacterial standard like penicillin. "We
use maggots and leeches in hospitals, so why not
clay?" Haydel asks.
The ASU duo have just received a substantial grant
from the National Institutes of Health that will allow
them to examine the mechanisms that allow two clays
mined in France to heal Buruli ulcer, a flesh-eating
bacterial disease found primarily in central and
western Africa. Buruli ulcer (related to leprosy) is
caused by Mycobacterium ulcerans, which produces a
toxin and destroys the fatty tissues under the skin.
It was recently declared to be "an emerging public
health threat" by the World Health Organization (WHO).
"The toxin is immunosuppressant; the patients feel no
pain and the body mounts no response to infection. It
leads to disfigurement, isolation, not unlike that
seen in leprosy," Haydel explained. "Traditional
antibiotics can only make a difference at the very
earliest stages of the disease, so treatments have, in
the past, been largely confined to amputations or
surgical excision of the infected sites." Haydel and
Williams believe that the French clay may represent a
new form of treatment, one that goes beyond the
capabilities of existing antibiotics.
The new research was sparked by health clinics on the
Ivory Coast that had been using two French clays to
successfully treat Buruli ulcer. The startling results
impressed the WHO, but the lack of supporting
scientific studies meant that funding for the
initiative was refused. Ivory Coast doctor, Thierry
Brunet de Courssou, who had been using the clays, then
put out a call for help which Williams and Haydel
responded to. "I answered a posting on the Clay
Mineral Society's listserve placed by Thierry. He was
asking to have someone take high resolution scanning
electron micrographs of the clays," Williams explains.
Williams not only took the micrographs of the
minerals, she went a step further and examined their
crystal structure and chemical compositions. She then
recruited Haydel who brought more than 13 years of
experience with pathogenic bacteria, in particular
tuberculosis, to the project. "I approached this work
from the viewpoint of a clinical microbiologist,"
Haydel says. "I ordered bacterial strains that
pharmaceutical companies use to test their
antimicrobials."
The duo tested both of the French clays that Brunet de
Courssou had been using. One completely inhibited
pathogenic Escherichia coli, Salmonella typhimurium,
Pseudomonas aeruginosa and Mycobacterium marinum. It
was also found to partially inhibit the growth of
pathogenic Staphylococcus aureus, including a
multi-drug resistant variety. But results from the
other clay weren't so exciting. "The other clay
actually helps the bacteria to grow," Haydel lamented.
The researchers don't know why one clay kills bacteria
and the other promotes growth.
Clay is a mineral with a crystalline structure that
Williams likens to a peanut butter and jelly sandwich.
The "bread" is composed of three regions, two silicate
layers with tetrahedral rings bounding an octahedral
core. The "peanut butter" is the charged cations, for
example, potassium, that stick to the negatively
charged tetrahedral ring surface. And the jelly?
Mainly organic compounds, says Williams. The
interlayer, as the peanut butter and jelly are termed,
can vary in width and composition depending on the
kinds of waters and elements present when it was
formed. It is this interlayer where much of the
elemental variability between clays can be found.
In the case of the two French clays, the chemical
structures are almost identical, but the different
trace element chemistry of the interlayer records an
older geologic condition, from a time when the
antimicrobial property was likely inherited.
Preliminary results suggest that while the
antibacterial activity is associated with the
interlayer, crystal size and structure also seem to
play a role. Haydel and Williams hope that their
continuing research will lead to a better
understanding of the clay's unique properties.
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