in vitro Activity of Hydrogen Peroxide and Hypochlorous Acid Generated by Electrochemical Scaffolds Against Planktonic and Biofilm Bacteria.

Hydrogen peroxide (H ₂ O ₂ ) and hypochlorous acid (HOCl) are biocides used for cleaning and debriding chronic wound infections, which often harbor drug resistant bacteria. Here, we evaluated the in vitro activity of H ₂ O ₂ and HOCl against 27 isolates of eight bacterial species involved in wound infections. Minimum inhibitory concentrations (MICs) and minimum biofilm bactericidal concentrations (MBBCs) were measured. When compared to their respective MICs, MBBCs of isolates exposed to H ₂ O ₂ were 16- to 1,024-fold higher and those exposed to HOCl were 2- to 4-fold higher. We evaluated selection of resistance after exposure of Staphylococcus aureus and Pseudomonas aeruginosa biofilms to 10 iterations of electrochemically generated HOCl or H ₂ O ₂ delivered using electrochemical scaffolds (e-scaffolds), observing no decrease in anti-biofilm effects with serial exposure to e-scaffold-generated H ₂ O ₂ or HOCl. 24-hour exposure to H ₂ O ₂ -generating e-scaffolds consistently decreased colony forming units (CFUs) of S. aureus and P. aeruginosa biofilms by ∼5.0-log ₁₀ and ∼4.78-log ₁₀ through 10 iterations of exposure, respectively. 4-hour exposure to HOCl-generating e-scaffolds consistently decreased CFUs of S. aureus biofilms by ∼4.9-log ₁₀ , and 1-hour exposure to HOCl-generating e-scaffolds consistently decreased CFUs of P. aeruginosa biofilms by ∼1.57-log ₁₀ These results suggest that HOCl has similar activity against planktonic and biofilm bacteria, whereas the activity of H ₂ O ₂ is less against biofilm than planktonic bacteria, and that repeat exposure to either biocide, generated electrochemically under the experimental conditions studied, does not lessen antibiofilm effects.
(Copyright © 2021 American Society for Microbiology.)