Targeting biofilms of multidrug-resistant bacteria with silver oxynitrate
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abstract
A topical antimicrobial, silver oxynitrate (Ag7NO11), has recently become available that exploits the antimicrobial activity of ionic silver but has enhanced activity because highly oxidised silver atoms are stabilised with oxygen in a unique chemical formulation. The objective of this study was to use a multifaceted approach to characterise the spectrum of antimicrobial and antibiofilm activity of a wound dressing coated with Ag7NO11 at a concentration of 0.4 mg Ag/cm2. Physiochemical properties that influence efficacy were also evaluated, and Ag7NO11 was found to release a high level of Ag ions, including Ag2+ and Ag3+, without influencing the pH of the medium. Time-kill analysis demonstrated that a panel of multidrug-resistant pathogens isolated from wound specimens remained susceptible to Ag7NO11 over a period of 7 days, even with repeated inoculations of 1 × 106 CFU/mL to the dressing. Furthermore, established 72-h-old biofilms of Pseudomonas aeruginosa, Staphylococcus aureus and two carbapenem-resistant Gram-negative bacteria (blaNDM-1-positive Klebsiella pneumoniae and blaVIM-2-positive P. aeruginosa) were disrupted and eradicated by Ag7NO11 in vitro. Ag7NO11 is a proprietary compound that exploits novel Ag chemistry and can be considered a new class of topical antimicrobial agent. Biocompatibility testing has concluded Ag7NO11 to be non-toxic for cytotoxicity, acute systemic toxicity, irritation and sensitisation.
