Bacterial biofilms are notably resistant to antibiotic. It has been found that the addition of a weak continuous electric direct current (DC) to the liquid surrounding the biofilm can increase the efficacy of the antibiotic. This phenomenon, known as the bioelectric effect, has only been partially elucidated.
The aim of this study was to confirm the DC bioelectric effect with Escherichia coli biofilms treated with either gentamycin or with oxytetracycline. After this confirmation the DC was replaced by radiofrequency current at 10 MHz with the same effective intensity as the DC. At this frequency there is no transport of ions between the electrodes, no creation of new ions, and no electrolysis.
|current density||60 A/m²||unspecified||unspecified||-||-|
The differences between the treated groups and the control groups in both sets of experiments (DC and radiofrequency) are significant. The DC data are substantially the same as those reported in other studies of the DC bioelectric effect. In the radiofrequency experiments also a synergy effect between radiofrequency current and the antibiotics was observed. The phenonmen, which is less prononuced than that found in the DC experiments, is interesting because the proposed explanations of the DC bioelectric effect (transport of ions within the biofilm, production of additional biocides by electrolysis, etc.) do not seem to be applicable. The authors suggest that this new phenomenon may be due to a specific action of the radiofrequency electromagnetic field upon the polar parts of the molecules forming the biofilm matrix.