A comparison of the antimicrobial efficacy of two silver-containing wound dressings on burn wound isolates

Abstract

To evaluate and compare the efficacy of a silver alginate (SA) dressing and a silver carboxymethyl cellulose (SCMC) dressing on burn isolates grown within the quasi/non-biofilm state and the biofilm phenotypic states. Antimicrobial activity was tested using 46 burn wound isolates with a corrected zone of inhibition (CZOI) assay on agar (quasi/non-biofilm) and poloxamer (biofilm). All Gram-negative and positive isolates evaluated were found to be sensitive to both silver containing wound dressings, although superior antimicrobial activity was observed for a select number of specific bacteria when grown in the quasi/non-biofilm phenotypic state, for the SCMC dressing. However, the majority of isolates demonstrated reduced sensitivity to silver when grown as a biofilm, compared with growth in the quasi/non-biofilm phenotypic state. Both dressings demonstrated equivalent antimicrobial activity on Gram-negative isolates grown in the biofilm phenotypic state. For the Gram-positive isolates growing in the biofilm phenotypic state, there appeared to be greater sensitivity to the SA dressing compared with the SCMC dressing, although this result was not statistically significant. This study demonstrated the antimicrobial effectiveness of an SA and SCMC dressing in inhibiting the growth of burn isolates residing in both the quasi/non-biofilm and biofilm phenotypic states. It also suggests the SA dressing could be more effective on Gram-positive isolates grown in the biofilm phenotypic state, compared with SCMC dressing.