In the presence of high frequency AC electric fields, the membrane of cells become polarized and store charge; thereby acting like electrical capacitors. This capacitance at the cellular level contributes to the overall “bulk capacitance” of the suspension (net charge stored in the interior). Therefore, as the cells proliferate, the suspension’s bulk capacitance (Cb) will increase. By measuring the increase of the bulk capacitance in blood culture samples, the presence of viable microorganisms can be quantified much more rapidly than currently available technologies.