Laboratory Research
Biofilm infection commonly complicates wound healing. Persister bacteria are a subpopulation of transiently antibiotic-tolerant bacterial cells that are able to resume growth after a lethal stress. Mechanisms underlying biofilm formation of such subpopulation of bacteria are different than those understood for the general bacterial population1. Extracellular DNA (eDNA) is a principal constituent within the biofilm matrix. While DNase treatments have demonstrated efficacy in eradicating standard biofilms, they are ineffective against persister biofilms. We reported that a DNase resistant biofilm of Pseudomonas aeruginosa (PAO1DwspF strain) can be disrupted by aurine tricarboxylic acid (ATA), a chemical inhibitor of covalent binding between eDNA and protein. In the current study, we incorporated ATA into a polymer-based gel* to develop a novel dressing (GelATA) that was tested against polymicrobial persister biofilm infection in a preclinical porcine burn wound model.
Methods: Eight 2x2 inches full thickness burn wounds were created on the dorsum of female Yorkshire pigs (70-80lbs; n=5) using a standardized method published by us. The wounds were inoculated with persister biofilm strains of clinical isolates of P. aeruginosa (PAO1DwspF) and Staphylococcus aureus (SArexB). Wounds were treated with either a standard-of-care dressing (SoC)† or GelATA once weekly. At D28 post-burn, GelATA treated wounds was switched to the gel dressing* alone (excluding ATA) until D56. Progression of burn wound healing was followed using non-invasive imaging, digital images, ultrasound imaging, and measurement of trans-epidermal water loss (TEWL). Histopathology and scanning electron microscopy (SEM) of the burn wound tissue biofilm were performed at D56.
Results: SEM imaging of GelATA treated wounds showed disrupted biofilm formation with limited bacterial colonization compared to SoC. Furthermore, GelATA significantly (p< 0.05) enhanced wound closure and re-epithelialization of persister biofilm-infected wounds (p< 0.05). Interestingly, improved wound closure with inhibition of biofilm formation resulted in functional healing which was evident by significant decrease in TEWL (p< 0.05) signifying improved restoration of skin barrier function.
Discussion:
This work presents first pre-clinical evidence for the efficacy of GelATA in disrupting persister wound biofilm and promoting functional wound closure in a pre-clinical porcine burn wound model.