MECHANISMS OF THE BACTERICIDAL ACTIVITY OF LOW AMPERAGE ELECTRIC-CURRENT (DC)

The mechanisms whereby low amperage (10-100 mu A) electric current (DC ) is bactericidal were investigated with Staphylococcus epidermidis an d Staphylococcus aureus. A zone of inhibition test involving the inser tion of an anode and cathode into an agar plate inoculated with a lawn of bacteria was used to study the antimicrobial activity of electric current. A zone of inhibition was produced around the cathode when 10 mu A (DC) was applied for 16 h. The diameter of the zone was greatly r educed in the presence of catalase. There was no zone around the catho de when the test was carried out under anaerobic conditions. H2O2 was produced at the cathode surface under aerobic conditions but not in th e absence of oxygen. A salt-bridge apparatus was used to confirm that H2O2 was produced at the cathode and chlorine at the anode. The antimi crobial activity of low amperage electric current under anaerobic cond itions and in the absence of chloride ions against bacteria attached t o the surface of a current carrying electrode was also investigated. A ntibacterial activity was reduced under anaerobic conditions, which is compatible with the role of H2O2 as a primary bactericidal agent of e lectricity associated with the cathode. A reduction in chloride ions d id not significantly reduce the antibacterial activity suggesting that chlorine plays only a minor role in the bactericidal activity towards organisms attached to anodal electrode surfaces. The localized produc tion of H2O2 and chlorine and the intrinsic activity due to electric c urrent may offer a useful method for eradicating bacteria from cathete r surfaces.