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How to Kill Germs, and Consumer Resistance

EARLIER this year, Dr. Boni E. Elewski told me a story that has made it impossible for me to go barefoot.

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AP

Dr. Elewski, a professor of dermatology at the School of Medicine at the University of Alabama, Birmingham, once tested bedroom carpets in hotels as she scouted for foot fungi (the micro-organisms that can flake off our skin and reside among carpet fibers). She found so many different microbes that she stopped categorizing hotels as being three or four stars. Instead, she now gives them three or four spores.

So, when hoteling, I wear socks religiously as my little piece of body armor. And how about you — where do you locate your inner Howard Hughes? Do you carry hand sanitizer around like a talisman? Wear gloves on buses or subways? Press elevator buttons with your knuckles? Eschew bowls of candy next to restaurant cash registers? Roll up your pants two hem lengths before entering a public lavatory or use paper towels to open the door on the way out?

In a world where the norovirus travels by cruise ship and the swine flu can hop a plane, we have become a country with germ compulsions, a nation of microbephobes. Still, bacteria have learned to outsmart antibiotics, and Pure Bioscience, a company based in El Cajon, Calif., says it is counterattacking with an even smarter biocide.

The company developed a molecule called silver dihydrogen citrate, or S.D.C., that it bills as an all-purpose germ killer. Hungry germs are attracted to the citrate part of the molecule, which they recognize as a food source. Then microscopic particles of ionized silver, an antimicrobial agent, emerge and destroy the germ cells.

Tradition is found here: silver has been used since the days of the ancient Greeks to purify water containers. And silver dihydrogen citrate turns out to be a pretty effective killer of certain viruses, bacteria and fungi.

In the United States, the Environmental Protection Agency has registered it as a disinfectant — a substance that wipes out the entire population of a given micro-organism — for hard surfaces like countertops. The molecule, used in a consumer product called PureGreen 24, can kill off salmonella and listeria in 30 seconds, according to the product label; it needs 10 minutes to eliminate athlete’s foot, the rhinovirus and the Hong Kong flu. In Europe, meanwhile, where regulators have approved silver dihydrogen citrate as an antimicrobial agent for personal care products, Beiersdorf has introduced antiperspirants and deodorants called Nivea for Men Silver Protect.

But even as swine flu looms large this fall, people are skeptical about a new antimicrobial substance that can eliminate both methicillin-resistant Staphylococcus aureus, or MRSA, and the bacteria behind body odor.

“It’s not such a miracle,” says Michael Krall, the chief executive of Pure Bioscience. “It does one thing really good: It kills bugs. But when you introduce a new technology, you are going up against some very large resistance.”

Indeed, it turns out that humans have something in common with bacteria that have learned how to resist antibiotics. As much as we want to control germs, we have learned to resist the idea of a more powerful disinfectant. What if it kills off so many microbes that we lose our natural ability to fight germs? What if some bacteria begin to resist the allure of citrate? What if the pico-sized — that is, smaller than a nanometer — silver ions have downstream effects? What if we fear a smarter germ killer as much as, or more than, we fear the germ itself?

Mr. Krall has two answers to all of this: science and live demonstrations.

Nationally known laboratories have run batteries of tests on silver dihydrogen citrate, which Pure Bioscience has posted on its Web site. Skeptics can read the results for themselves. For those who like more tangible evidence, Mr. Krall is wont to open wide and spray the stuff in his mouth to demonstrate his belief in its safety.

SOME cruise lines are testing the disinfectant offshore against the norovirus, Mr. Krall says. Some jails and schools have started using it to keep flu and infections at bay. And, last month, Pure Bioscience formed a partnership with a new pharmaceutical company created by doctors at the Cleveland Clinic. The nascent company hopes to use the antimicrobial agent to develop over-the-counter and prescription drugs to combat the microorganisms that cause acne, toenail fungus and athlete’s foot.

It will take a few years, however, for the company to go through the clinical trial process and submit the results for product approval by the Food and Drug Administration. Until then, when I travel, I am keeping my socks on.