There is a new line of defense against MRSA, the dangerous antibiotic-resistant bacteria. Paint. A team has developed a coating that effectively and specifically kills species of the bacterium Staphylococcus, including MRSA (methicillin-resistant Staphylococcus aureus). In tests where the coating was mixed with latex paint, walls covered with the paint killed 100% of all MRSA applied to them.

Other possible uses for the coating include surgical masks and medical instruments.

Because of the way lysostaphin kills bacteria, they do not stick to the wall, and can be washed off, so the surface does not become clogged.

The coating relies on an enzyme called lysostaphin. First discovered in 1964, the enzyme is already commercially available in large quantities. In nature, the enzyme is produced and secreted by one species of Staphylococcus and is lethal to most other Staphylococcus species. It works by punching holes in the bacterial cell wall, literally opening up the bacterium.

The enzyme alone forms a poor coating. The researchers at Rensselaer Polytechnic Institute overcame this problem by attaching the enzyme to tiny carbon tubes. These tubes are called nanotubes because they are about one nanometer (a billionth of a meter) in diameter. Carbon nanotubes are strong and flexible, both stabilizing the enzyme and concentrating it. Once bound to the nanotubes, the enzyme can be added to a polymer, such as paint, to form an effective bacteria killing coating. The flexibility of the nanotubes also allows the enzyme some mobility, allowing it to reach the bacteria more easily.

Previous attempts at using bactericidal coatings have come up against several problems. Some coatings have been toxic to humans or animals, leaching harmful chemicals into the environment and simultaneously losing effectiveness. Other coatings have tended to clog quickly, also losing effectiveness.

Lysostaphin-containing paint shows none of these drawbacks. It's only toxic to staphylococci. Because of the way it kills bacteria, they do not stick to the wall, and can be washed off, so the surface does not become clogged.

The researchers also claim that it is unlikely that MRSA will be able to develop resistance to a naturally-occurring enzyme.

One researcher enthusiastically endorsed the coating: "Here we have a system where the surface contains an enzyme that is safe to handle, doesn't appear to lead to resistance, doesn't leach into the environment, and doesn't clog up with cell debris. The MRSA bacteria come in contact with the surface, and they're killed."

There's no word yet on whether MRSA-killing paint will be available only in standard institutional colors.

An article detailing the research was published in the July 27, 2010 issue of ACS Nano.