Aurine Tricarboxylic Acid (ATA) Disrupts DNase-Resistant Wound Biofilm Formed by Persister Clinical Isolate Bacteria

BACKGROUND: Biofilms represent a major threat to health care, and it is a clinical challenge to manage infected wounds resistant to antibiotic. Persistent bacterial phenotypes such as small colony variants (SCV) are a subpopulation of antibiotic-tolerant bacterial cells that are often slow-growing or growth-arrested and can resume growth after a lethal stress. The key to managing biofilms of persistent bacteria is complete eradication and one approach is to dismantle the structural framework of these biofilms. Extracellular DNA (eDNA) is a major component of the biofilm. DNase treatments are known to eradicate standard biofilms but are ineffective against persister biofilms. Unlike PAO1, PAO1_wspF released fragmented eDNA from live cells. Fragmented eDNA, thus released, was responsible for resistance of PAO1_wspF biofilm to disruption by DNase. We report that DNase resistant biofilm made up of rugose SCV can be disrupted by a chemical inhibitor (ATA) of covalent binding between eDNA and protein.

METHODS: With industry partnership, a novel wound care dressing (GelATA) was developed to test its efficacy in treatment of persister biofilm model. GelATA is conventional polymer-based gel dressing* containing ATA. To develop the preclinical persister burn wound biofilm model, eight 2”x2” full thickness burn wounds were made on the dorsum of (70-80lbs) female domestic white pigs (n=4). Polymicrobial SCV biofilm infection was established with P.aeruginosa (PAO1 _wspF) and Staphylococcus Aureus (S. aureus rexB) both which are clinical isolates. Wounds were treated with either placebo dressing (Acticoat) or GelATA once weekly.

RESULTS: ATA was effective in disrupting biofilm made up of hyperbiofilm SCV P.aeruginosa (PAO1_wspF) in vitro. Biofilm infection with standard non-SCV PA01 and USA3000 (S. aureus) allows wounds to re-epithelialize on d56 post wounding. However, such response was further delayed in case of SCV biofilm infection demonstrating the additional pathogenic significance of these persister bacteria. Progression of burn wound healing is currently followed for functional wound closure.

CONCLUSIONS: This is the first work involving biofilm infection of persister bacteria (P. aerugionsa and S. aureus) testing ATA for its efficacy in disrupting DNAse resistant biofilm in a pre-clinical porcine burn wound model.