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Cutting-Edge Plastic Cleans Up

Antibacterial polymer keeps on killing surface, and air, germs

TUESDAY, May 22, 2001 (HealthDayNews) -- Put a killer on a leash, and it'll just keep eradicating all those bad bacteria on everything from your telephone to your countertops.

Scientists say they have created a new plastic that can coat surfaces and wipe out airborne bacteria while staying attached to the surface by a "thread" so it can keep on killing germs.

The new polymer, which could be used on myriad surfaces, may be a boon to anyone looking to prevent infection by such potentially dangerous microbes as Staphylococcus aureus or Escherichia coli. Some strains of both S. aureus and E. coli can cause severe bouts of food poisoning.

"This polymer has been synthesized by my colleagues at the Massachusetts Institute of Technology, and we came up with an idea to create a molecule that is based on an antiseptic molecule that will not only attach to a surface but be able to kill bacteria," says co-author Kim Lewis, an associate professor at Tufts University's Chemical and Biological Engineering Laboratory in Boston. "What we wanted was to create a surface that would be permanently sterile that could be used on countertops and the like."

Lewis says the group had to surmount the problem of attaching an antiseptic molecule to a surface while also giving it the ability to invade a cell and kill it. "We came up with the simple idea that if we attach this antiseptic molecule to the surface with a long thread, then the molecule will be able to penetrate a bacteria cell and remain attached [to the surface] to be able to kill again," he says.

The new polymer, called hexyl-PVP, was able to kill up to 99 percent of staph, Pseudomonas and E. coli, all of which are common in household and hospital infections, Lewis says. The coating was tested by spraying concentrated solutions of bacteria on glass slides that were coated with the plastic. The results were then compared with samples of wood, plastic, metal and ceramic sprayed with the bacteria.

Anywhere from 94 percent to 99 percent of the staph bacteria were killed, Lewis says. For Pseudomonas and E. coli, "there was at least 100-fold killing of the bacteria when compared to the other surfaces. The polymer does not get rid of all of the bacteria," he adds.

And it doesn't create resistant bacteria, Lewis says. "For the bacteria to develop resistance, they would have to change their whole composition, and that is not possible with something that is delivered to the microbe on a thread," he explains.

The new polymer was announced today in the Proceedings of the National Academy of Sciences.

Lewis says that MIT has filed a patent on the new coating, but he has no idea when the product may come to market. "That will depend on the industry," he says.

But you may want to hold off thinking about coating your kitchen and bathroom with the plastic.

"There are two issues to my mind," says Cheryl Mendelson, author of the book Home Comforts: The Art and Science of Keeping House. "Simply because a material kills bacteria that comes directly in contact with it does not mean that would kill a bacteria that was two layers up, say in meat. I don't think it would make your food safe."

"You'd really have to learn how far the polymer helps and what it would do to your cleanliness habits. What changes would it require?" she asks.

While the coating may be a boon to hospitals or food production plants, Mendelson is not so sure it's appropriate in the home.

"Really, how necessary is this? One of the points I make in my book is that we really don't need antibacterials in the home. It is hard for me to imagine that this polymer would function as anything other than an adjunct to the kind of safety efforts in the home that experts already advise us."

For instance, you can simply use hot soapy water to clean cutting boards or other surfaces that touch food, and if you're really concerned, you can use a mild solution of bleach and water.

"The question is how much is it needed in the home, and how much would it cost?" Mendelson asks.

What To Do

For more on avoiding invading bacteria in the home, see Science and Technology News Network or Pfizer. Here's where to go if you're curious about staph, E. coli and other bugs. And here are some food handling safety tips from the Food and Drug Administration.

And don't forget these other HealthDay stories on resistant bacteria and food poisoning.

SOURCES: Interviews with Kim Lewis, Ph.D., associate professor, Tuft University's Chemical and Biological Engineering Laboratory, Boston, Mass.; Cheryl Mendelson, Ph.D., J.D., author Home Comforts: The Art and Science of Keeping House; May 22, 2001 Proceedings of the National Academy of Sciences
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