A Systematic Comparison of Antimicrobial Wound Dressings using a Planktonic Cell and an Immobilised Cell Model. Kamran

Aim: The aim of the study was to evaluate the ability of in-vitro planktonic and immobilised cell models for determining the antimicrobial efficacy of common antimicrobial wound dressings.

Methods and Results: Five strains of A.baumannii
, P.aeruginosa and S. aureus (MRSA) were tested against four antimicrobial wound dressings containing silver, honey or PHMB, using both a planktonic and immobilised cell model. Across all species and models used, the NSCD demonstrated the best antimicrobial activity being as good if not better than all the other dressings. The planktonic cell model was less effective at differentiating the dressings on antimicrobial performance as the immobilised cell model indicating that a diffusion barrier had a significant impact on the performance of some dressings. In the presence of the diffusion barrier antimicrobial impact of the Honey and PHMB dressings was significantly reduced particularly in the case of A. baumannii. Activity was at least an order of magnitude lower in the immobilised cell model vs. the planktonic cell model.

Conclusions: The use of a planktonic cell model within standard tests may overestimate the efficacy of honey and PHMB. The use of an immobilised cell model provides a more demanding test for antimicrobial dressings allowing dressing to dressing and pathogen to pathogen differences to be more clearly quantified. Significance and Impact of study: The introduction of planktonic and immobilised cell models as part of testing regimens for wound dressings will provide a more thorough understanding of their antimicrobial and antibiofilm properties.