A new approach

How impedance flow cytometry works

Flow cytometry involves measuring the characteristics of cells in a flow. Impedance flow cytometry is measuring cell characteristics in a flow using electrical impedance as a detection method. In SBTs technology, this is achieved by running the user’s sample through a microfluidic flow cell with integrated electrodes that can detect and assess any objects between 0.5 and 5 µm.

When an object flows between the electrodes in the flow cell, the magnitude of current running between the electrodes will change and an event is detected. The change in current is distinct for living cells since they conduct electricity differently than particles due to their intact cell membranes and cytoplasm. This enables our technology to accurately detect all bacterial cells in the sample while omitting particles and dead bacteria with non-intact membranes from the count. The result is an accurate count of Membrane Intact Cells per millilitre (MIC/ml) in just 3 minutes.

MIC is a direct measure of all the bacteria in the sample. This is a different approach from e.g. plate counts where only culturable bacteria are measured as Colony Forming Units (CFU).  Since some bacteria species grow better at different temperatures, at different ambient conditions, and on different nutritional media, and many do not grow on plates at all, the count in the same sample differs significantly between chosen growth conditions. As a result, most samples will usually show higher MIC than CFU, especially when a high fraction of non-culturable bacteria are present e.g. in natural waters. In contrast, in cases where all bacteria are culturable on plates, such as in bacteria fermentations or when working with pure cultures, the correlation between plate counting CFU and SBT's MIC is linear and approximately 1:1.

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