Linearity and correlation

If your sample vial follows the requirements, then you get both great linearity and low variance in the BactoBox® output.

Sample vial requirements

Proper output requires proper input. Make sure that your sample vial follows the requirements. See What can I measure on? and Sample preparation.

Disaggregate your cells

Some cells tend to form clumps (aggregates), which makes them too big to measure with BactoBox®. Use 3 mm glass beads and a vortex mixer to disaggregate the cells in your sample vial.

BactoBox® does not count particles outside the 0.5–5 µm range.

See Break up clumps and chains for other disaggregation methods.

Linearity

For active cultures, BactoBox® shows great linearity between both:

• BactoBox® cells/mL and the dilution factor

• BactoBox® cells/mL and plate counts (CFUs/mL)

This linearity covers the entire range given by the limits of detection.

The table below shows how BactoBox® performs across various particle types. Note that all R² values are very close to 1, which indicates strong linearity across the tested range.

Particle type	Tested range (1/mL)	Linearity with dilution factor	Linearity with plate counts
Staphyloccus epidermidis	30 000–5 000 000	R2=0.9975	R2=0.9982
1 µm silica microspheres	1 000 000–5 000 000	R2=0.9995	N/A

Correlation with plate counts

The figure below shows a direct comparison between plate count (CFUs/mL) to BactoBox® (cells/mL). Note that the solid lines (BactoBox®) closely follows the dashed lines (plate counts) across all tested bacterial species. This indicates a strong correlation between BactoBox® and plate counts.

The growth curves for five bacterial species. Plate counts (CFU/mL) in dashed lines and BatoBox® (ICC aka cells/mL) in solid lines.