A novel in vitro interkingdom wound biofilm model can support the growth of anaerobic bacteria

Background
Chronic wounds, such as diabetic foot ulcers, are commonly infected leading to recurrence and chronicity of the wounds, although this is not well characterised. We have previously developed a simple novel three-dimensional in vitro interkingdom wound biofilm model that has been used to characterise the response to wound washes. Here, the complexity of the model was increased to include anaerobes species found within our recent diabetic wound microbiome analysis.
MethodsThese biofilm consortia consisted of the yeast, Candida albicans, the aerobes, Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus hominis, Streptococcus agalactiae, and Corynebacterium simulans. The anaerobes included were Finegoldia magna, Anaerococcus vaginalis, Peptoniphilus gorbachii, Porphyromnas asacharolytica, and Prevotella buccalis. Biofilms were grown over a period of 9 days within a cellulose matrix hydrogel, with intermittent sampling. Compositional qPCR was used to enumerate each species within the biofilm. 
ResultsOverall, approximately 108 bacteria colonised the cellulose matrix, comprised of yeasts, aerobes and anaerobes. Aerobic bacteria were reduced by approximately 2 logs when the biofilm was grown in anaerobic conditions compared to 5% CO2 or aerobically (p<0.01). Bacterial species were shown to coaggregate with the yeast and hyphae, supporting their adhesion and biofilm formation.
ConclusionThe addition of anaerobes to the wound model further reflects the environment in vivo, allowing this model to be used for accurate testing of antimicrobial agents. The ability of C. albicans to support interkingdom interactions, as well as anaerobes in a non-anoxic environment may explain why we observe elevated levels of anaerobes in these diabetic wounds.