Antibiofilm efficacy of antimicrobial solutions in an in vitro artificial wound slough (AWS) and artificial wound eschar (AWE) biofilm Model.

Abstract: Aim: Necrotic wounds contain eschar and slough, which act as reservoirs for microorganisms and biofilms. Here, we evaluate the antibiofilm efficacy of two multifunctional metal complexes (MMC) and a commercial antibacterial product (PHMB) on two artificial would biofilm models comprised of eschar (AWE) and slough (AWS). Both models utilize key proteins found in necrotic tissue (collagen, fibrinogen, and elastin) and are distinguished by their water content, where AWS contained more than 90% water, while AWE contained less than 10% water. Method: A Pseudomonas aeruginosa biofilm was cultured in a 48 well plate for 24 hours, followed by the addition of eschar and slough layer on the top of biofilm. Both models were exposed to the antimicrobials for 24 hours, before being neutralised, enumerated to confirm total viability of the biofilm cultures. The disruption of the biofilm by the treatments was also imaged by LSM 780 Zeiss confocal microscope. Results / Discussion: Results showed significant differences in the antimicrobial efficacy of the antiseptics within the two models. In the AWE model, both MMCs, and the PHMB product achieved >6 log reductions in microbial cell density. However, in the AWS model only the MMCs achieved a 5 log reduction, with PHMB showing no significant reduction in cell density compared to an untreated control. Conclusion: These findings suggest that the efficacy of antimicrobial solutions is heavily influenced by wound exudate. The high-water content, shown for AWS, hindered antimicrobial activity possible due to a dilution or quenching affect.

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