Bacterial enumeration: beads versus CFU

Therese M. McGinn tmcginn at
Mon Nov 28 11:16:05 EST 2005

Hello All,


I have been using the Becton Dickinson Cell Viability Kit with Counting
Beads to determine numbers of live bacteria in cultures.  This method
involves staining with propidium iodide and thiazole orange to
discriminate live from dead cells.  Numbers of live cells are determined
by a simple calculation relating the number of events in the live gate
to the number of beads.  


We have been comparing the numbers of live cells by this method to
CFU/ml as determined by traditional enumeration assay.	The flow-based
method shows much higher numbers of live cells than the enumeration
assay.	I would appreciate any feedback or suggestions on how to
reconcile this discrepancy.  


Thank you for your consideration,


Terry McGinn



Therese M. McGinn Ph.D.

Senior Research Scientist

Benchmark Biolabs, Inc.

Phone: 402-475-8104

Fax: 402-475-8511


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