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What Makes a Natural Clay Antibacterial?

Posted by Shawna Cecilio on

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3126108/

This paper reports the geochemical characteristics of the most effective antibacterial clay we have identified; supplied by Oregon Mineral Technologies (OMT) Grants Pass, Oregon. The clay source is an open pit mine in hydrothermally altered, pyroclastic material in the Cascade Mountains. It was shown to completely eliminate Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella typhimurium, and antibiotic resistant extended-spectrum beta lactamase (ESBL) E. coli and methicillin resistant S. aureus(MRSA) within 24 h.

A variety of physical and/or chemical processes can make clays antibacterial. Physical bactericide can occur by surface attraction between clay minerals and bacteria, which can hamper passive and active uptake of essential nutrients, disrupt cell envelopes or impair efflux of metabolites. The natural antibacterial clays we have studied do not kill by physical associations between the clay and bacterial cells. The OMT clay shows no zone of inhibition when applied dry to bacterial colonies in vitro; however, the clays are antibacterial when hydrated. When an aqueous suspension of OMT clay (50 mg/mL water) was placed in dialysis tubing (25 000 MDCO) and submerged into a beaker of E. coli suspended in sterile Tryptic soy broth, the bacteria died over 24 h. Comparisons have been made between aqueous leachates of the OMT clay incubated withE. coli in nutrient broth and without nutrient broth to eliminate chemical speciation influenced by the broth chemistry. E. coli are completely killed by OMT leachates rapidly (Figure 1), compared to controls in distilled – deionized (DDI) water. Cell death occurs by exchange of soluble clay constituents toxic to the bacteria.


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