Evaluation of Treatment of Methicillin-ResistantStaphylococcus aureusBiofilms with Intermittent Electrochemically-Generated H₂O₂or HOCl

Abstract

Chronic wound infections can be difficult to treat and may lead to impaired healing and worsened patient outcomes. Novel treatment strategies are needed. This study evaluated effects of intermittently produced H2O2and HOCl, generated via an electrochemical bandage (e-bandage), against methicillin-resistant Staphylococcus aureus biofilms in an agar membrane biofilm model. By changing the working electrode potential, the e-bandage generated either HOCl (1.5 VAg/AgCl) or H2O2(-0.6 VAg/AgCl). The degree of biocidal activity of intermittent treatment with HOCl and H2O2correlated with HOCl treatment time; HOCl treatment durations of 0, 1.5, 3, 4.5, and 6 hours (with the rest of the 6 hour total treatment time devoted to H2O2generation) resulted in mean biofilm reductions of 1.36±0.2, 2.22±0.16, 3.46±0.38, 4.63±0.74 and 7.66±0.5 log CFU/cm2, respectively vs. non-polarized controls, respectively. However, application of H2O2immediately after HOCl treatment was detrimental to biofilm removal. For example, 3-hours HOCl treatment followed by 3-hours H2O2resulted in a 1.90±0.84 log CFU/cm2lower mean biofilm reduction than 3-hours HOCl treatment followed by 3-hours non-polarization. HOCl generated over 3-hours exhibited biocidal activity for at least 7.5-hours after e-bandage operation ceased; 3-hours of HOCl generation followed by 7.5-hours of non-polarization resulted in a biofilm cell reduction of 7.92±0.12 log CFU/cm2vs. non polarized controls. Finally, intermittent treatment with HOCl (i.e., interspersed with periods of e-bandage non-polarization) for various intervals showed similar effects (approximately 6 log CFU/cm2reduction vs. non-polarized control) to continuous treatment with HOCl for 3-hours, followed by 3-hours of non-polarization. These findings suggest that timing and sequencing of HOCl and H2O2treatments are crucial for maximizing biofilm control.