Researchers have identified a better method of using silver to treat infected wounds. They report their findings in the December 2010 issue of the journal Antimicrobial Agents and Chemotherapy.
Healing difficult wounds is often a challenge, due, in large part, to the bacterial biofilms that frequently thrive in wounds. Sixty-five percent of hospital-acquired infections involve biofilms, according to an estimate from the Centers for Disease Control and Prevention. Biofilms are far more resistant to antibiotics than bacteria which have not organized themselves in this manner. Certain silver preparations appear to improve antibiotic efficacy against wound infections.
Victoria Kostenko, and John Martinuzzi of the University of Calgary, Alberta, Canada, and their collaborators, concerned that laboratory studies testing the effectiveness of different silver preparations often fail to match observations from clinical studies, provide a new test procedure which corresponds more accurately to observations from clinical and animal studies. They also find that nanocrystaline silver has greater efficacy than conventional silver against biofilms during both one-day and long-term treatment.
The nanocrystaline silver boosts the vulnerability of biofilms to antibiotics as compared to larger silver particles because the small particles expose more surface. The silver atoms on those surfaces interact with macromolecules such as DNA and proteins within the biofilms, disorganizing them, thus degrading their defenses against antibiotics.
One of the advances in the testing methodology involves refreshing the growth media, thereby decreasing the bioavailability of silver particles, as happens in actual wounds as compounds therein bind with the silver particles, says Martinuzzi. That, he says, could be responsible for the discrepancy between laboratory results using standard protocols, and clinical results. "We hope our results will convince others to devise laboratory tests which better account for the wound environment. This will help advance product development."
Interestingly, this investigation grew out of the researchers' efforts to develop bioremediation for oil sands tailing ponds, such as those in northern Alberta. "Biofilms are highly adaptable to hostile environments and great producers of by-products, including surfactants capable of helping in the separation of residual bitumen and consolidation of clay suspensions," says Martinuzzi. "The underlying mechanisms are quite generic and thus we often transfer information between fields. We believe that exploiting biofilms will enable us to reduce the ecological footprint of oil sand operations to acceptable levels."
Reference: V. Kostenko, J. Lyczak, K. Turner, and R.J. Martinuzzi, 2010. Impact of silver-containing wound dressings on bacterial biofilm viability and susceptibility to antibiotics during prolonged treatment. Antim. Agents Chemother. 54:5120-5131.