Posters

Title:

Synthetic wound fluid modulates antibiotic susceptibility and biofilm formation in wound pathogens

Authors:

• Charlotte R. Morgan
• Aleyna Yarranton
• Lydia C. Powell

Abstract:

Background

Chronic non-healing skin wounds are a significant cause of morbidity and mortality in patients. Bacterial biofilm-related infections formed within these wounds impair tissue healing, resist conventional treatment and harbour multi-drug resistant bacteria. Conventional in vitro models fail to replicate the wound microenvironment, limiting translational relevance. This study investigated the use of synthetic wound fluid (SWF) as a clinically relevant medium to more accurately model infection processes in chronic wounds and inform the development of effective treatments.

Methods

Chronic wound bacterial isolates of Pseudomonas aeruginosa PAO1 and Methicillin-resistant Staphylococcus aureus (MRSA) 1004a were grown in multiple recipes of synthetic wound fluid (SWF), comprised of either fetal bovine serum (FBS), human-derived serum or bovine serum albumin (BSA) in comparison to a standard laboratory media, Mueller Hinton Broth (MHB). Growth kinetics were monitored over 24 hours and antimicrobial susceptibility was assessed using minimum inhibitory concentrations (MIC) assays. Biofilm architecture was analysed via confocal laser scanning microscopy with COMSTAT quantification. Atomic force microscopy (AFM) and electrophoretic light scattering (ELS) were employed to assess the mechanical properties and surface charge of the wound isolates.

Results

FBS-based SWF supported the robust growth of both P.aeruginosa and MRSA, whereas while BSA-based SWF reduced proliferation. Unexpectedly, MRSA grown in both FBS-based and human serum-based SWF exhibited increased antimicrobial susceptibility to the antibiotic of last resort, colistin, compared to MHB, resulting in a reduced MIC value (16 µg/ml vs 256 µg/ml). Biofilm analysis revealed significant alterations in P. aeruginosa and MRSA biofilm biomass and dead/live bacterial ratio when grown in FBS-based SWF in comparison to MHB (p < 0.05). AFM and ELS assays also revealed alteration of the cellular mechanical properties and bacterial surface charge when grown in FBS-based SWF, in comparison to MHB (p < 0.05).

Conclusions

SWF markedly influences growth, antimicrobial response, and biofilm characteristics of chronic wound pathogens. By providing a physiologically relevant model, this approach enhances understanding of infection dynamics in chronic wounds and informs the development of targeted therapeutic strategies.

References:

• ¹ González et al. (2018) Pathog Dis 76:fty023 https://doi.org/10.1093/femspd/fty023

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