INOCULUM STANDARDIZATION

BactoBox®

Standardize your inoculum with confidence

Top view of BactoBox device
Stock

2.41 × 108cells/mL

Dilute

1 : 241

Dose

1.0 × 106cells/mL

THE PROBLEM

Your plate count does not match the dose you planned

You set the dose from OD or McFarland. The plate count arrives one to seven days later, and it is off.

You plan the dose1 × 106CFU/mL, set from OD
1–7
days later
The plate says4 × 106CFU/mL4× the plan

THE SOLUTION

Count the cells before you dose

  1. 1Dilute your stock

    Into the measuring range

  2. 2Measure

    About two minutes

  3. 3Calculate

    The dilution to your target dose

  4. 4Dose

    At the concentration you planned

Doses are set from the measured stock, not read directly.

When you must commit to a dose before the experiment runs

Dosing animals and larvae

Mice, fish or insect larvae. Know the dose on the day you infect.

Setting an MOI

On cell lines, organoids and tissue models.

Preparing test suspensions

For challenge and efficacy tests in development work.

WHY OD FAILS YOU

Dilute to the same OD, and you get a different dose

One OD unit does not hold a fixed number of cells. In LB, one OD unit of E. coli holds 5 × 108 to 2 × 109 cells/mL, depending on when the culture is caught.

YOU CATCH THE CULTURE ATYOU DILUTE TOYOU DOSECELLS/MLOD 0.4OD 0.14.9 × 10⁷0.6×OD 1.5OD 0.18.1 × 10⁷1.0×OD 3.3OD 0.11.6 × 10⁸2.0×OD 4.4OD 0.12.0 × 10⁸2.5×Planned dose, from a calibration at OD 1.5VS PLAN

E. coli in LB, one culture sampled as it grew. In an active culture, cells/mL tracks CFU/mL. SBT Instruments data.

WHY IT WORKS

A count that agrees with your plates, in two minutes

In an active culture, the cells we count are the cells that form colonies.

BactoBox cell counts plotted against CFU/mL for six bacterial species, lying on the 1:1 line
BactoBox® cell counts against CFU/mL for six bacterial species, through growth and early stationary phase. Data from Jordal et al. 2025. Read the article →
Gram-positive
Gram-negative
Aerobes
Anaerobes

Measure cultures above 107 cells/mL.

Two ways to have an active culture when you need it

Subculture in the morning

Measure a few hours later, in exponential phase.

Seed the overnight culture

So it is still active when you arrive.

PROOF

Peer-reviewed studies that already set their dose with BactoBox

Nature Communications 2025

Mice

Counted L. reuteri to set the oral dose in germ-free mice, in a study of the gut and behaviour.

Park et al., POSTECH, South Korea

PNAS 2026

Insect larvae

Set the S. aureus inoculum for Galleria mellonella killing assays.

Mattingly et al., Emory University, United States

Gastroenterology 2025

Human cells

Counted F. prausnitzii to standardise the dose for stimulating human monocytes.

Danne et al., Sorbonne Université, France

GOOD TO KNOW

Frozen, dried or stored stock

Holds cells that no longer form colonies, so the count and CFU differ. Grow an active culture first.

Organisms that clump

Get in touch, and we will look at your organism with you.

Try it on your next inoculum

Protocols in the help center →