Influence of human acute wound fluid on the antibacterial efficacy of different antiseptic polyurethane foam dressings: An in vitro analysis

Abstract

Treating infected acute and/or chronic wounds still represents a major challenge in medical care. Various interactions of antiseptic dressings with wound environments regarding antimicrobial efficacy remain unclear. Therefore, this work aimed to investigate the influence of human acute wound fluid (AWF) on the antimicrobial performance of different antiseptic foam dressings in vitro against typical bacterial wound pathogens. Eight antiseptic polyurethane foam dressings containing either a silver formulation or a polyhexamethylene-biguanide (PHMB) were assessed regarding their antimicrobial potency against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa using a modified time-kill assay based on ISO EN 20743. The antiseptic efficacy was evaluated standardly as well as under the influence of human AWF after 2, 4, 6, and 24 hours. The specific chemical formulation and concentration of the antiseptic substance (ionic or nanocrystalline silver, silver sulfadiazine, PHMB 0.1%/0.5%) embedded within the dressings seemed to play a key role. For certain dressings (two nanocrystalline and one ionic silver dressing), the antimicrobial efficacy was significantly reduced under the influence of AWF compared to unchallenged test series. Unchallenged the efficacy of PHMB was comparable to silver against P. aeruginosa and even significantly superior against S. aureus and E. coli. Challenged with AWF the reduction rates for silver adjusted or even exceeded (P. aeruginosa) those of PHMB. Within a challenging wound environment, especially some silver formulations demonstrated a reduced bacterial reduction. Regarding the presented in vitro results, the biomolecular interactions of antiseptic wound dressings with wound fluid should be part of more extensive investigations, considering varying factors such as bacterial species and wound (micro)environment to develop targeted therapeutic regimes for the individual.

In vitro Activity of Antimicrobial Wound Dressings on P. aeruginosa Wound Biofilm

“…The relevance of its chemical structure has already been proven in previous studies. The loss of efficacy was pointed out for nanocrystalline silver (Gnanadhas et al, 2013;Rembe et al, 2018) more than for ionic silver, however, interactions with the wound microenvironment such as pH value or protein content have been described for both several times (Hirsch et al, 2011;Kapalschinski et al, 2013;Wiegand et al, 2015;Rembe et al, 2018). This emphasizes the need for human-adapted analyses in vitro, as the here tested dressing containing ionic silver demonstrates an overall loss of antimicrobial efficacy in a complex, protein-rich, human-adapted microenvironment.…”

Antimicrobial Hypochlorous Wound Irrigation Solutions Demonstrate Lower Anti-biofilm Efficacy Against Bacterial Biofilm in a Complex in-vitro Human Plasma Biofilm Model (hpBIOM) Than Common Wound Antimicrobials

“…The development of the hpBIOM ( Figures 4A – C ; Besser et al, 2019 , 2020 ) aimed to narrow the gap between in-vitro and in-vivo biofilm research and provides a translational approach. The use of a complex biofilm model based on human material, including plasma and immune cells, addresses the interactions of microbial biofilms with the human wound micro-environment ( James et al, 2008 ; Percival et al, 2015 ), as well as the relevant loss in efficacy of antiseptics and antimicrobials under challenging conditions ( Rembe et al, 2018 ; Radischat et al, 2020 ).…”

Anti-biofilm activity of antimicrobial hypochlorous wound irrigation solutions compared to common wound antiseptics and bacterial resilience in an innovative in-vitro human plasma biofilm model (hpBIOM)

“…4a-c) (10,11), aims to narrow the gap between in-vitro and in-vivo biofilm research and provide a translational approach. The use of a complex biofilm model based on human material, including plasma and active immune cells, addresses the interactions of microbial biofilms with the human wound environment (3,14) as well as the relevant efficacy loss of antimicrobials under challenge (23,24), providing a 'close-to-reality' test scenario.…”