Summary
Abstract
The purpose of this study was to investigate the mechanism by which a direct electrical current reduced the viability of Staphylococcus epidermidis biofilms in conjunction with ciprofloxacin at physiologic saline conditions meant to approximate those in an infected artificial joint. Biofilms grown in CDC biofilm reactors were exposed to current for 24 hours in 1/10th strength tryptic soy broth containing 9 g/L total NaCl. Dose-dependent log reductions up to 6.7 log10 CFU/cm2 were observed with the application of direct current at all four levels (0.7 to 1.8 mA/cm2) both in the presence and absence of ciprofloxacin. There were no significant differences in log reductions for wells with ciprofloxacin compared to those without at the same current levels. When current exposures were repeated without biofilm or organics in the medium, significant generation of free chlorine was measured. Free chlorine doses equivalent to the 24 hour endpoint concentration for each current level were shown to mimic killing achieved by current application. Current exposure (1.8 mA/cm2) in medium lacking chloride and amended with sulfate, nitrate, or phosphate as alternative electrolytes produced diminished kills of 3, 2, and 0 log reduction, respectively. Direct current also killed Pseudomonas aeruginosa biofilms when NaCl was present. Together these results indicate that electrolysis reactions generating hypochlorous acid from chloride are likely a main contributor to the efficacy of direct current application. A physiologically relevant NaCl concentration is thus a critical parameter in experimental design if direct current is to be investigated for in vivo medical applications.
Study details
- Published in: PloS one 8.2 (2013): e55118
- Microbes studied: Staphylococcus epidermidis
Source
Source: PloS one 8.2 (2013): e55118
Conditions tested
| Parameter | Value |
|---|---|
| Organisms | Biofilms, Staphylococcus spp. |
| Publication | PloS one, 2013 |
Reading this responsibly
Published figures are obtained under controlled conditions, usually on clean surfaces or in defined matrices. Organic load, surface condition, temperature and application coverage all affect real-world performance. Use these numbers to design a protocol, then validate it on your own site with environmental swabbing.
Applying it
Concentrations in this range are within the adjustable output of every EcoloxTech commercial system, so implementing this protocol is a settings question rather than a procurement one. Where the claim needs to sit on a registered label, see HOCl-AS200, EPA Reg. No. 101112-1.