Hydrogel dressing containing natural extracts inhibits dual-species biofilms of Staphylococcus aureus and Acinetobacter baumannii in ex vivo wound infection models

Wound infections represent a significant cause of delayed wound healing. An active wound dressing was developed by incorporating extracts of Rhodomyrtus tomentosa leaf and Quercus infectoria gall in a carboxymethyl cellulose hydrogel (RQ hydrogel). In a modified artificial wound bed mimicking chronic wound infections, RQ hydrogel could inhibit up to 7 log CFU/mL of pathogens in both single- and dual-species biofilms. Antibacterial efficacy was further assessed in three different ex vivo porcine skin wound infection models. Model I: Ex vivo skin infection, the skin was exposed to dual cutures of Staphylococcus aureus/Acinetobacter baumannii. Topical application of RQ hydrogel resulted in 5 log CFU/mL reduction within 6 h. Model II: Ex vivo burn wound infection, more than 3 log CFU/mL of dual-species cultures were inhibited after treatment with RQ hydrogel. Model III: Ex vivo biofilms, preformed biofilms were established by culturing the pathogens on pig skin for 24 h in culture media containing wound exudates, followed by the application of RQ hydrogel on the preformed biofilms. Reduced bacterial biofilms were observed as indicated by decreased fluorescence intensity. Moreover, scanning electron microscopy confirmed the ex vivo inhibitory effects of RQ hydrogel.