Are silver nanoparticles a miracle solution against microbes?



Antimicrobials are used to kill or slow the growth of bacteria, viruses and other microorganisms. They can be in the form of antibiotics, used to treat infections in the body, or as an additive or coating on commercial products used to repel germs. These vital tools are essential for preventing and treating infections in humans, animals and plants, but they also pose a global threat to public health when microorganisms develop resistance, a concept known as resistance. antimicrobials.

One of the main drivers of antimicrobial resistance is the overuse and overuse of antimicrobial agents, including silver nanoparticles, a cutting-edge material with well-documented antimicrobial properties. It is increasingly used in commercial products with improved germ killing performance – it has been woven into textiles, applied to toothbrushes, and even mixed into cosmetics as a preservative.

The Gilbertson Group at the Swanson School of Engineering at the University of Pittsburgh, used laboratory strains of E. coli to better understand bacterial resistance to silver nanoparticles and to try to anticipate the potential abuses of this material. The team recently published their results in Nature Nanotechnology.

“Bacterial resistance to silver nanoparticles is under-studied, so our group looked at the mechanisms behind this event,” said Lisa Stabryla, lead author of the article and recently graduated with a doctorate in civil and environmental law at Pitt. “This is a promising innovation to add to our arsenal of antimicrobials, but we need to consciously study it and perhaps regulate its use to avoid decreased efficacy as we have seen with some common antibiotics.”

Stabryla exposed E. coli at 20 consecutive days of silver nanoparticles and monitoring bacterial growth over time. Nanoparticles are about 50 times smaller than a bacteria.

“At first the bacteria could only survive at low concentrations of silver nanoparticles, but as the experiment continued we found that they could survive at higher doses,” he said. noted Stabryla. “Interestingly, we found that bacteria developed resistance to silver nanoparticles, but not to their released silver ions alone.”

The group sequenced the genome of E. coli who had been exposed to silver nanoparticles and found a mutation in a gene that corresponds to an efflux pump that pushes heavy metal ions out of the cell.

“It is possible that some form of silver will enter the cell, and when it arrives, the cell mutates to pump it out quickly,” she added. “More work is needed to determine whether researchers can possibly overcome this resistance mechanism through particle design.”

The group then studied two different types of E. coli: a hyper-motile strain that swims in its environment faster than normally motile bacteria and a non-motile strain that has no physical means to move. They found that only the hyper-mobile strain developed resistance.

“This finding could suggest that silver nanoparticles may be a good option for targeting certain types of bacteria, especially non-motile strains,” Stabryla said.

Ultimately, bacteria will always find a way to evolve and escape antimicrobials. The hope is that an understanding of the mechanisms that drive this evolution and a conscious use of new antimicrobials will reduce the impact of antimicrobial resistance.

“We are the first to examine the effects of bacterial motility on the ability to develop resistance to silver nanoparticles,” said Leanne Gilbertson, assistant professor of civil and environmental engineering at Pitt. “The observed difference is really interesting and merits further investigation to understand it and how to link the genetic response – the regulation of the efflux pump – to the bacteria’s ability to move through the system.

“The results are promising in being able to adjust the properties of the particles for a desired response, such as high efficiency while avoiding resistance.”

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