Differentiation of viable and non-viable bacterial biofilms using electrorotation.

A new technique for studying the properties of biofilms has been developed, based on the phenomenon of electrorotation. Biofilms of Klebsiella rubiacearum were formed on the surfaces of 6 microns diameter polystyrene beads, and the presence of such films was found to alter their electrorotation spectra. The effects of adding a biocide (polyhexanide) to the surrounding aqueous medium was also investigated. The dielectric properties of the beads with biofilms, before and after biocide treatment, were interpreted from the electrorotation spectra using modelling methods that have been well tested for other heterogeneous biological systems. The technique is of value in understanding the physico-chemical properties of biofilms and can be adapted for monitoring the presence of toxic chemicals and for testing the activity of biocides against biofilms.