An in Vitro Assessment of the Antimicrobial Performance of Silver-Containing Gelling Fiber Wound Dressings Using Multi-Species CDC Reactor and Colony Drip-Flow Bioburden Models

Aim: To assess the efficacy of five silver-containing gelling fiber wound dressings in vitro against pre-formed 72-hour multi-species surface-attached cultures of wound pathogens, Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans, using adapted UKAS-accredited Centers for Disease Control (CDC) reactor and colony drip-flow (CDF) models. 

Method: Cultures of S. aureus, P. aeruginosa and C. albicans were used to inoculate a CDC reactor and a CDF model. The systems were incubated with flow for 72 hours at 37°C. Following incubation, surface-attached cultures were washed to remove planktonic microorganisms. CDC reactor and CDF coupons were sandwiched between 4 cm x 4 cm sections of hydrated silver-containing wound dressings (Dressing A through E) for 24 hours (CDC reactor) or 72 hours (CDF).

Results/Discussion:  An average of ~7.0 Log and ~6.5 Log total viable microorganisms were recovered from untreated CDC reactor and CDF controls, respectively. No viable microorganisms were recovered from coupons following treatment with Dressing A when surface-attached cultures were established in either the CDC reactor or the more wound care-relevant CDF. 

Conclusion: There is an increasing need to introduce clinically-relevant and independently-validated test models to evaluate the antimicrobial effectiveness of wound care products. The use of mixed-species models better mimics the complex microbiology of chronic wounds, and the presence of C. albicans decreases the susceptibility of P. aeruginosa to antimicrobials compared to treatment in a single-species model. Dressing A demonstrated superior antimicrobial efficacy, compared to other silver-containing gelling fiber dressings, in both of these challenging multi-species bioburden test models.