Aims: To determine the potential use of flow cytometry for viability asssessment of freeze-dried bacterial cells.
Methods and results: Escherichia coli CIP 54.8T and Vibrio metschnikovii CIP 104262 were analysed. The viability of freeze-dried cells resuspended in a nutrient broth was evaluated by culture whereas activity was determined by flow cytometry analysis of both esterase activity and cell death. Activity assessment by flow cytometry was found to be a rapid and good indicator of cell viability and was very efficient for quality control. For V. metschnikovii the fraction of active cells varies greatly depending on the freeze-drying procedure and within a given procedure.
Conclusions, significance and impact of the study: Bacterial activity assessment by flow cytometry is very efficient for the control of freeze-dried cells.