Concentrate your sample

It is generally not recommended to use BactoBox® for measuring samples with very low bacterial concentrations. This page is a collection of tips and tricks for how to do so.

Too low bacterial concentration

Samples with low concentration are usually transparent.

Your sample must have at least 30 000 cells/mL to measure it with BactoBox®.

Very low bacterial concentration?

BactoBox® is generally not suitable for very low bacterial concentrations.

My sample stock contains around 100 000 cells/mL

This is just above the lower limit of detection but not by a lot.

Theoretically, your sample is good to go since the cells/mL concentration is well above the threshold. In practice, however, you must both:

• Hit the right electrical conductivity

• Reach the minimum sample volume of 4 mL

Already achieved both? Well, then you're done! Otherwise, this is where it gets a bit tricky. See:

Hit the right conductivity

Specifically the section about low dilution factors.

My sample stock is below the limit of detection

You must concentrate your sample before you measure on it with BactoBox®. We recommend that you use a centrifuge together with membrane filter. We describe this filter-centrifugation approach here:

Filter-centrifuge your sample

Motivation

BactoBox® counts individual particles. If there are too few particles, the concentration estimate is too uncertain. If there are too many particles, we can't tell them apart. Therefore, we have limit of detection (LoD). BactoBox® outputs concentrations in these ranges:

• 30 000–5 000 000 cells/mL (3·10⁴ to 5·10⁶ cells/mL)

• 30 000–5 000 000 total/mL (3·10⁴ to 5·10⁶ total/mL)

See limits of detection for more details.