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.
