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Updated: Jul 16, 2026
Imaging Flow Cytometry to Study Microbial Autoaggregation
Published on: September 29, 2023
Description and validation of a rapid (1 h) flow cytometry test for enumerating thermophilic bacteria in milk powders
1Fonterra Research Centre, Palmerston North, New Zealand. steve.flint@fonterra.com
Aims:
The aim of this study was to develop a rapid assay for enumerating thermophilic bacteria in milk powder.
Methods And Results:
The BactiFlow flow cytometer was used to count bacteria based on esterase activity in viable bacterial cells. A protocol for total viable bacteria was modified by heat-treating the sample to selectively label thermophilic bacteria. Samples of milk powder dissolved in 0.1% peptone were treated with 0.8% ethylenediaminetetraacetic acid to reduce background interference because of denatured milk proteins. Either thermophilic bacteria were added to the dissolved milk powder or milk powder solutions were incubated at 55 degrees C for 2-3 h to enrich the natural thermophile population for testing. Results from the BactiFlow were compared with traditional plate count results.
Conclusions:
Thermophilic bacteria in milk powder can be enumerated within 1 h using the BactiFlow flow cytometer.
Significance And Impact Of The Study:
Microbiological test results obtained within 1 h can potentially be used to monitor manufacturing processes, effectively trace problems and provide confidence in the manufacture of product.
