Abstract
BackgroundThe increasing prevalence of bacterial infections that are resistant to antibiotic treatment has caused the scientific and medical communities to look for alternate remedies aimed at prevention and treatment. In addition to researching novel antimicrobials, there has also been much interest in revisiting some of the earliest therapies used by man. One such antimicrobial is silver; its use stretches back to the ancient Greeks but interest in its medicinal properties has increased in recent years due to the rise in antibiotic resistance. Currently antimicrobial silver is found in everything from lunch boxes to medical device implants. Though much is claimed about the antimicrobial efficacy of silver salts the research in this area is mixed.MethodsHerein we investigated the efficacy of silver acetate against a carbapenem resistant strain of Acinetobacter baumannii to determine the in vitro activity of this silver salt against a World Health Organisation designated category I critical pathogen. Furthermore, we use the Galleria mellonella larvae model to assess toxicity of the compound and its efficacy in treating infections in a live host.ResultsWe found that silver acetate can be delivered safely to Galleria at medically relevant and antimicrobial levels without detriment to the larvae and that administration of silver acetate to an infection model significantly improved survival. This demonstrates the selective toxicity of silver acetate for bacterial pathogens but also highlights the need for administration of well-defined doses of the antimicrobial to provide an efficacious treatment.
Highlights
The use of silver as an antimicrobial has been described throughout recorded history (Alexander, 2009) and though its popularity waned with the development and widespread use of antibiotics from the 1940’s, the increasing global prevalence of antibiotic resistance amongst bacterial pathogens has reignited interest in this ancient remedy
Silver acetate demonstrates antimicrobial activity against A. baumannii To first demonstrate the antimicrobial activity of silver acetate five strains of A. baumannii were tested to determine the minimum inhibitory and bactericidal concentrations of Standard minimum inhibitory concentration (MIC) and Minimum bactericidal concentrations (MBCs) assays were performed against a range of A. baumannii strains grown in Mueller– Hinton Broth in a 96-well plate
We sought to determine the antimicrobial efficacy of silver acetate against a carbapenem resistant strain of A. baumannii both in vitro and in an in vivo G. mellonella infection model
Summary
The use of silver as an antimicrobial has been described throughout recorded history (Alexander, 2009) and though its popularity waned with the development and widespread use of antibiotics from the 1940’s, the increasing global prevalence of antibiotic resistance amongst bacterial pathogens has reignited interest in this ancient remedy. Despite its apparent popularity as an antimicrobial, the efficacy of silver treatments has met with mixed results in the research community (Chopra, 2007; Politano et al, 2013) and manufacturer efficacy claims are often difficult to verify due to a lack of access to raw data Given these limitations on determination of antimicrobial activity, there is clear evidence that more independent data is needed to better understand the antibacterial activity of silver compounds currently in use for treatment of infection. Results: We found that silver acetate can be delivered safely to Galleria at medically relevant and antimicrobial levels without detriment to the larvae and that administration of silver acetate to an infection model significantly improved survival This demonstrates the selective toxicity of silver acetate for bacterial pathogens and highlights the need for administration of well-defined doses of the antimicrobial to provide an efficacious treatment
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