Electric field induced desorption of bacteria from a conditioning film covered substratum

Desorption of three oral bacterial strains from a salivary conditioning fil m on an indium tin oxide electrode during application of a positive (bacter ial adhesion to the anode) or a negative electric current was studied in a parallel plate flow chamber. Bacterial adhesion was from a flowing suspensi on of high ionic strength, after which the bacterial suspension was replace d by a low ionic strength solution without bacteria and currents ranging fr om -800 to +800 muA were applied. Streptococcus oralis J22 desorbed during application of a positive and negative electric current with a desorption p robability that increased with increasing electric current. Two actinomyces strains, however, could not be stimulated to desorb by the electric curren ts applied. The desorption forces acting on adhering bacteria are electroos motic in origin and working parallel to the electrode surface in case of a positive current, whereas they are electrophoretic and electrostatic in ori gin and working perpendicular to the surface in case of a negative current. By comparison of the effect of positive and negative electric currents, it can be concluded that parallel forces are more effective in stimulating ba cterial desorption than perpendicular forces. The results of this study poi nt to a new pathway of cleaning industrial and biomedical surfaces without the use of detergents or biocides. (C) 2001 John Wiley & Sons, Inc.