Antimicrobial activity of a bioelectric dressing using an in vitro wound pathogen colony drip-flow reactor biofilm model.

OBJECTIVE: We performed in vitro antibiofilm testing of a silver and zinc containing microcurrent generating bioelectric dressing (BED) against clinical wound pathogens to determine its efficacy in preventing biofilm formation under low shear and continuous flow conditions, simulating wound infection environments.

METHOD: We customised an in vitro colony drip-flow reactor (DFR) biofilm model for efficacy evaluation of BED. Each bacterial pathogen was diluted to 10(4)CFU/ml and inoculated on the polycarbonate filter membrane as an abiotic support. BED and controls (no treatment, gauze, and blank polyester with no silver and zinc) were applied directly on the membranes where bacterial cultures were inoculated. Biofilms were continuously developed onto the membranes for 72 hours at room temperature. Biofilm formation was confirmed by crystal violet staining and microscopic observation. Through vigorous shaking and sonication, the released bacteria were serially diluted, plated, and incubated for 24 hours at 37°C to determine the numbers of surviving bacteria.

RESULTS: Biofilms were well developed onto blank polyesters, but not the BED after 72 hours incubation. Crystal violet staining from the blank polyesters showed large and fully grown biofilms. We observed an inhibition in bacterial growth on BED treatment. The antibiofilm activity of the BED against each of eight monospecies biofilms showed a 1- or 2 log10 (or 10- or 100-fold) reduction in bacterial numbers compared with those of controls.

CONCLUSION: Our results demonstrated that colony DFR biofilm model was an appropriate for testing the antibiofilm efficacy of BED under low shear and continuous flow conditions for simulating clinical wound environments. The bioelectric currents generated from the silver and zinc active ingredients in the dressing resulted in antibiofilm activity of this wound care device.