Today, most commercialized technology to directly detect bacteria requires either staining, fluorescence, or incubation. SBT Instruments offers a new affordable product, which can perform very rapid measurements of the bacteria level in aqueous solutions with no pretreatment of the sample, no incubation time, and no advanced user interaction. This is accomplished by using impedance flow cytometry. The technology is based on an electrical detection principle, where impedance measurements are used to detect particles and bacteria on a single cell basis.

Working Principle

The working principle behind impedance flow cytometry is simple. An aqueous solution is circulated through a microfluidic flow cell that has integrated electrodes. Bacteria and particles transition across the electrodes, which results in a change in impedance. The impedance change for bacteria is uniquely different compared to other non-organic particles, and it is therefore possible to provide a very accurate estimate of both the bacteria and particle count in the sample in real-time. The working principle detects all bacteria species in the liquid sample, as every bacteria will result in a corresponding impedance change when they enter the system. The unit of measurement for our benchtop prototype device is therefore total bacteria count per milliliter (bacteria/ml).

What is total bacteria count?

SBT Instruments uses the technology of impedance flow cytometry (IFC) to electrically detect all bacteria and other particles in aqueous solutions, while simultaneously differentiating the bacteria from the other particles. This makes it the perfect tool for quantitatively assessing the bacteria count in a liquid sample. We do not operate in secondary units such as relative light units or enzymatic reaction times, which may differ from measurement to measurement and from system to system. Instead we operate in actual bacterial counts that can not be misinterpreted.


Total bacteria count vs. total plate count

Total plate counts (TPC) has been the standard method for measuring bacteria for hundreds of years, but it has certain flaws. Most notably, the response time is notoriously slow, typically 24–72h. Additionally, only a fraction of the bacteria is actually counted during a TPC because different bacteria species grow better at different temperatures and on different nutritional media. The typical unit used for TPC counts is CFU, short for colony forming unit, which indicates how many bacteria formed colonies on the specific plate and at the specific temperature used. There is an effect typically referred to as the great plate count anomaly, which states that the actual number of bacteria in a sample is usually 100x-1000x larger than what the total plate count suggests. SBT Instruments measures the unique electrical footprint of every bacteria, and is therefore able to count all bacteria in a sample. This means that the concentrations measured by benchtop prototype device are usually orders of magnitude higher than a corresponding TPC count and therefore also gives a much more accurate view of the bacterial content of the sample.