Abstract
Biofilms are major contributors to delayed wound healing and there is a need for clinically relevant experimental models to assess theranostics. Microorganisms release volatile organic compounds (VOCs) and the ability to identify these in infected cutaneous wounds could lead to efficient non-invasive diagnosis. The aims here were to develop and assess bacterial biofilm formation and identify their VOC profiles in an in vitro model and validate in human ex vivo incisional and excisional cutaneous wound models. Biofilm development was assessed using multiple microscopy techniques with biofilm-forming deficient controls and quantified using metabolic and biomass assays; and VOC production measured by gas chromatography-mass spectrometry. The production of most VOCs was affected by biofilm development and model used. Some VOCs were specific either for planktonic or biofilm growth. The relative abundance of some VOCs was significantly increased or decreased by biofilm growth phase (P < 0.05). Some Staphylococcus aureus and Pseudomonas aeruginosa VOCs correlated with biofilm metabolic activity and biomass (R ≤ −0.5; ≥0.5). We present for the first time bacterial biofilm formation in human ex vivo cutaneous wound models and their specific VOC profiles. These models provide a vehicle for human skin-relevant biofilm studies and VOC detection has potential clinical translatability in efficient non-invasive diagnosis of wound infection.
Highlights
Biofilms are defined as complex microbial communities embedded in a protective self-produced biopolymer matrix, which provides protection against antimicrobial agents and host defence mechanisms[1]
Methicillin-sensitive Staphylococcus aureus ATCC 29213 (MSSA) showed early signs of biofilm formation, with the presence of viable bacteria interspersed between dead cells and limited extracellular matrix (ECM) on day 1 (Fig. S1A,B)
MSSA biofilms matured by day 5, evident as areas of heavily concentrated, mainly viable bacteria surrounded by ECM and containing a mixture of dead cells and extracellular DNA stained red
Summary
Biofilms are defined as complex microbial communities embedded in a protective self-produced biopolymer matrix, which provides protection against antimicrobial agents and host defence mechanisms[1]. Clinicians rely heavily on clinical wound characteristics for the diagnosis of infection[10]. Identification of VOCs in cutaneous wound infections could provide a non-invasive and effective method of diagnosis prior to the onset of gross malodour or obvious tissue reaction and damage. No previous studies have utilised human ex vivo incisional and excisional cutaneous wound models for bacterial biofilm formation, providing relevance to surgical and open wound cutaneous defects, respectively. Nor has VOC detection been utilised in the diagnosis of cutaneous wound infections. The aims here were to develop and assess bacterial biofilm formation and identify their unique VOC profiles in an in vitro model and validate these using human ex vivo incisional and excisional cutaneous wound models.
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