United States. Researchers at Northwestern University warn that antimicrobial paints could be doing more harm than good.
In a new study, researchers tested bacteria commonly found in homes in samples or drywall coated with synthetic, antimicrobial latex paints. Within 24 hours, all the bacteria died, except for Bacillus timonensis, a spore-forming bacterium. Most Bacillus commonly inhabit soil, but many are found indoors.
"If you attack bacteria with antimicrobial chemicals, then they will mount a defense," said Erica Hartmann of Northwestern, who led the study. "Bacillus is usually harmless, but if you attack it, you could cause it to develop more antibiotic resistance."
Bacteria thrive in warm, humid environments, so most die on indoor surfaces, which are dry and cold, anyway. This makes Hartmann question the need to use antimicrobial paints, which may be causing bacteria to become stronger.
Spore-forming bacteria, such as bacillus, protect themselves by remaining dormant for a period of time. While idle, they are highly resilient even in the harshest conditions. After those conditions improve, they are reactivated.
"When it's in the form of spores, you can hit it with everything you have, and it's still going to survive," said Hartmann, an assistant professor of civil and environmental engineering in Northwestern's McCormick School of Engineering. "We need to be judicious in our use of antimicrobial products to make sure we're not exposing the most harmless bacteria to something that could make them harmful."
The study was published online April 13 in the journal Indoor Air.
One problem with antimicrobial products, such as these paints, is that they are not tested against the most common bacteria. Manufacturers test how well more pathogenic bacteria, such as E. coli or Staphylococcus, survive, but largely ignore the bacteria that people (and the products they use) would most plausibly find.
"E. coli is like the 'lab rat' of the microbial world," Hartmann said. It is much less abundant in the environment than people think. We wanted to see how true indoor bacteria would respond to antimicrobial surfaces because they don't behave in the same way as E. coli."
The study, "Impacts of Interior Surface Finishes on Bacterial Viability," was supported by the Alfred P. Sloan Foundation (Award Number G-2016-7291) and the Searle Leadership Fund.
Data Source Provider: Northwestern University.
