Bacteria adapt and evade nanosilver's sting

A new study has shown that while silver nanoparticles effectively killed E.coli cells, they also caused another bacteria (Bacillus sp.) to rapidly adapt and flourish.

Researchers from UNSW have cautioned that more work is needed to understand how micro-organisms respond to the disinfecting properties of silver nano-particles, increasingly used in consumer goods, and for medical and environmental applications.

Although nanosilver has effective antimicrobial properties against certain pathogens, overexposure to silver nano-particles can cause other potentially harmful organisms to rapidly adapt and flourish, a UNSW study reveals. This result, published in the journal Small, could have wide-reaching implications for the future use of nanosilver as an antimicrobial agent with biomedical and environmental applications.

"We found an important natural ability of a widely occurring bacteria to adapt quite rapidly to the antimicrobial action of nanosilver. This is the first unambiguous evidence of this induced adaptation," says co-author Dr Cindy GunawanUsing an experimental culture, UNSW researchers observed that nanosilver was effective in suppressing a targeted bacteria (Escherichia coli), but that its presence initiated the unexpected emergence, adaptation and abnormally fast growth of another bacteria species (Bacillus).

The efficacy of nanosilver to suppress certain disease-causing pathogens has been well-documented, and as a result, it has become widely used in medicine to coat bandages and wound dressings. It also has environmental uses in water and air purification systems, and is used in cosmetics and detergents, and as a surface coating for things like toys and tupperware.