Antibiofilm Activity of Novel Silver Complex in Dressings and Gels Against Drug Resistant Microorganisms

Introduction: Previous studies demonstrated that Ag5IO6 coated onto dressings1 and incorporated into wound gels2 has rapid anti-planktonic activity, broad-spectrum anti-adherence longevity, and efficacy against mature biofilms, including when compared to other commercially avail- able silver wound dressings and gels. This study tested Ag5IO6-coated dressings against C. auris, an emerging antimicrobial-resistant fungus causing a serious global health threat, and various antimicrobial-resistant bacteria. Methods: Ag5IO6 was coated onto three non-adhesive wound dressings at varying concentrations. Anti-Adherence Testing: Dressings were preconditioned in saline for 0, 1, 7, 14, or 28 days (changes 3x/week) and challenged with methicillin resistant Staphylococcus aureus (MRSA, USA 400), coagulase negative Staphylococcus epidermidis (CoNS, ATCC 35984), vancomycin resistant Enterococcus faecalis (VRE, ATCC 51575), Candida auris (CDC B11903) and Acinetobacter baumannii (ATCC 17978) at 105 CFU/mL in appropriate media in 0.9% saline containing 25% human serum (HS - most strains) or 10 g/L bovine serum albumin (A. baumannii), for 24h (35°C, 110 rpm). Dressings were then placed in neu- tralizer (supplemented Dey-Engley broth), and sonicated for 30 minutes to dislodge adhered biomass. Challenge media was also neutralized for planktonic organism recovery. Colony forming units (CFU) of both ad- hered and planktonic microorganisms were enumerated by culture-based methods. Anti-biofilm Testing: Dressings were tested against pre-formed biofilms of the microorganisms listed above using a modification of ASTM E27993. Mature biofilms were challenged with 1-2 dressing discs in appropriate media containing 25% HS for 24h (35°C, 110 rpm), and recovered as above. Results: All Ag5IO6-coated dressings showed strong anti-adherence and anti-planktonic activity against all microorganisms up to 7 days. At 14-28 days, there was some drop-off in activity with some concentra- tion-microorganism combinations, but many combinations still demon- strated ongoing bactericidal activity up to 28 days. In antibiofilm testing, high-concentration Ag5IO6-coated dressings demonstrated consistent elimination of mature biofilms and surrounding planktonic microorgan- isms with 1 or 2 discs, with the exception of C. auris biofilms and 1 disc against A. baumannii biofilm. Medium-concentration dressings showed bactericidal activity against some microorganisms, while the lowest con- centration did not achieve log 3 reductions. Discussion: In general, Ag5IO6 coated onto wound dressings demon- strated strong anti-adherence and antibiofilm activity against antibiot- ic-resistant microorganisms.