Silver side: Antibacterial gel

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  • Published: Oct 15, 2016
  • Channels: Atomic
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Silver antibacterials

This SEM depicts a couple of clusters of aerobic Gram-negative, non-motile Acinetobacter baumannii bacteria as seen under a magnification of 12,739x.. Public domain: sourced,_SEM,_9330_lores.JPG

Flame atomic absorption spectrometry (FAAS) has been used to study silver nanoparticles being tested as antibacterial agents against resistant strains of bacteria, including Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa, and Staphylococcus aureus.

Science has known that bacteria can evolve resistance to antibiotics for almost as long as we have been using these drugs to treat infection. However, we have managed to rail against natural selection in pathogenic organisms by developing new drugs that defeat the defences of those bacteria, at least we had until recently. Antibiotics are widely used and often inappropriately, whether a course is not finished because symptoms disappear or there is insufficient supply for a full prescription or else when a healthcare worker prescribes them for non-bacterial disease. There is also the problem of inappropriate self-medication in parts of the world where antibiotics are available over-the-counter or over-the-internet.

Urgent protection

Writing in the journal Molecules Klebson Silva Santos, Andriele Mendonça Barbosa, Luiz Pereira da Costa, Malone Santos Pinheiro, and Francine Ferreira Padilha of the Institute of Technology and Research, at Tiradentes University, in Aracaju, Brazil, and Maria Beatriz Prior Pinto Oliveira of the University of Porto, Portugal, explain how alternatives to conventional antibiotics are urgently needed to protect us from often-lethal bacterial infection. They say that, "Silver nanocomposites can be an alternative strategy to avoid Gram-positive and Gram-negative bacteria growth, including multidrug-resistant strains."


The team has used a biosynthetic process to convert silver nitrate solution into silver nanoparticles through the natural action of a fermented medium of Xanthomonas species, proteobacteria that are known to cause disease in various plants. The culture produces a xanthan gum polymer containing the silver nanoparticles which were investigated using transmission electron microscopy (TEM), showing spherical nanoparticles smaller than 10 nanometres in diameter. The team evaluated silver ion content using FAAS and found that 1 gram of silver nanocomposite would contain almost 50 micrograms of silver.

500milligrams of silver nanocomposite was then tested against various strains of multidrug resistant bacteria and two, Pseudomonas aeruginosa and Acinetobacter baumannii, taken from hospital patients. All bacterial strains were sensitive to the presence of the silver nanocomposite failing to grow within a 10 to 13 millimetre inhibition zone.

"The biosynthesized silver nanocomposite seems to be a promising antibacterial agent for different applications, namely biomedical devices or topical wound coatings," the team concludes.

Related Links

Molecules 2016, 20, E1255: "Silver Nanocomposite Biosynthesis: Antibacterial Activity against Multidrug-Resistant Strains of Pseudomonas aeruginosa and Acinetobacter baumannii"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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