MECHANISM OF ELECTRICAL ENHANCEMENT OF EFFICACY OF ANTIBIOTICS IN KILLING BIOFILM BACTERIA

The bioelectric effect, in which electric fields are used to enhance t he efficacy of biocides and antibiotics in killing biofilm bacteria, h as been shown to reduce the very high concentrations of these antibact erial agents needed to kill biofilm bacteria to levels very close to t hose needed to kill planktonic (floating) bacteria of the same species . In this report, we show that biofilm bacteria are readily killed by an antibiotic on all areas of the active electrodes and on the surface s of conductive elements that lie within the electric field but do not themselves function as electrodes. Considerations of electrode geomet ry indicate that very low (<100 mu A/cm(2)) current densities may be e ffective in this electrical enhancement of antibiotic efficacy against biofilm bacteria, and flow experiments indicate that this bioelectric effect does not appear to depend entirely on the possible local elect rochemical generation of antibacterial molecules or ions. These data a re expected to facilitate the use of the bioelectric effect in the pre vention and treatment of device-related bacterial infections that are caused by bacteria that grow in biofilms and thereby frustrate antibio tic chemotherapy.