Antimicrobial efficacy of modern wound dressings: Oligodynamic bactericidal versus hydrophobic adsorption effect

Abstract Locally infected wounds and wounds colonised with multidrug-resistant bacteria are commonly treated with local antimicrobial agents. Recently, wound dressings have been introduced into clinical practice that reduces bacteria by adsorbing bacteria on the dressing surface by a hydrophobic effect. Our aim was to investigate, whether this hydrophobic effect is only present in dressings coated with dialkyl carbamoyl chloride (DACC) or also in other modern wound dressings. To determine the hydrophobicity of the dressing surface contact angle measurements were performed. In addition, for selected wound dressings, the bacteria eliminating effect of the wound dressings for Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa were measured. 31 of the 34 wound dressings presented with a hydrophobic surface. The reduction factor (RF) of one wound dressing without coating was 1.6 for MRSA and RF 2.1 for P. aeruginosa . One with a DACC coated dressing showed a RF of 0.7 (MRSA) and 1.2 ( P. aeruginosa ). The RF of a wound dressing that releases silver ions was 6.1 for MRSA and 7.5 for P. aeruginosa respectively. The results show that both uncoated and with DACC coated wound dressings can have hydrophobic surfaces. These hydrophobic dressings are able to adsorb bacteria onto their surface and consequently remove them from the wound. However, the RF for wound dressings that release silver ions is significantly higher. Depending on the degree of contamination, these results can have an effect on the clinical decision to choose certain products. We assume that for e.g. infected or critically colonised wounds, wound dressings with a hydrophobic effect may not be sufficient to significantly improve the microbiological wound condition. However, this assumption has to be verified in clinical studies.