Clay minerals may offer an answer to MRSA, other superbug infections

Common in Africa, Buruli ulcers start as painful skin swellings. Then infection leads to the destruction of skin and large, open ulcers on arms or legs.

Delayed treatment — or treatment that does not work — may cause irreversible deformities, restriction of joint movement, widespread skin lesions, and sometimes life-threatening secondary infections.

Treatment with daily applications of green clay poultices healed the infections. “These clays,” says Williams, “demonstrated a unique ability to kill bacteria while promoting skin cell growth.”

Unfortunately, the original French green clays were depleted. Later testing of newer samples did not show the same results.

Research on French green clays, however, spurred testing of other clays with likely antibacterial properties.

To date,” says Williams, “the most effective antibacterial clays are those from the Oregon deposit.”

Samples from an area mined by Oregon Mineral Technologies (OMT) proved active against a broad spectrum of bacteria, including methicillin-resistant S. aureus (MRSA) and extended-spectrum beta-lactamase-resistant E. coli (ESBL).

What’s in those rocks?
Understanding the geologic environment that produces antibacterial minerals is important for identifying other promising locations, says Williams, “and for evaluating specific deposits with bactericidal activity.”

The OMT deposit was formed near volcanoes active over tens to hundreds of thousands of years. The Crater Lake region is blanketed with ash deposits from such volcanoes.

OMT clays may be 20 to 30 million years old. They were “born” eons before deposits from volcanoes such as Mt. Mazama, which erupted 7,700 years ago to form the Crater Lake caldera.

Volcanic eruptions over the past 70,000 or so years produced silica-rich magmas and hydrothermal waters that may have contributed to the Oregon deposit’s antibacterial properties.

To find out, Williams and Morrison took samples from the main OMT open pit. Four types of rocks were collected: two blue clays, and one white and one red “alteration zone” rock from the upper part of the deposit.

Blue clay to the rescue
The OMT blue samples were strongly bactericidal against E. coli and S. epidermidis. The OMT white sample reduced the population of E. coli and S. epidermidis by 56 percent and 29 percent, respectively, but the red sample didn’t show an antibacterial effect.

We can use this information to propose the medicinal application of certain natural clays, especially in wound healing,” says Williams.

Chronic, non-healing wounds, adds Morrison, are usually more alkaline (vs. acidic) than healthy skin. The pH of normal skin is slightly acidic, which keeps numbers of bacteria low.

Antibacterial clays can buffer wounds to a low [more acidic] pH,” says Williams, like other accepted chronic wound treatments, such as acidified nitrate. “The clays may shift the wound environment to a pH range that favors healing, while killing invading bacteria.”

The Oregon clays could lead to the discovery of new antibacterial mechanisms, she says, “which would benefit the health care industry and people in developing nations. A low-cost topical antibacterial agent is quickly needed.”

Answers to Buruli ulcers, MRSA and other antibiotic-resistant infections may lie not in a high-tech lab, but in ancient rocks forged in a hot zone: Oregon’s once — and perhaps future — volcanoes.