Flow cytometry analysis of the activity of disinfecting agents tested with Staphylococcus aureus and Escherichia coli.

The efficacy of five disinfecting agents was tested by a new microbiological method, i.e. the flow cytometry. The method is based on kinetic measurements of the effects of a disinfecting agent on the percent of live/dead cells detected with propidium iodide. E. coli ATCC52922 strain and S. aureus ATCC 29213 strain were used in the experiment. From the measurements the killing time 50 (KT50) was estimated as the period of time needed to kill 50% of microorganisms in the disinfected volume. KT50 for ethanol 70% was 11s and it was the most efficient disinfecting agent among all examined. Other commercial preparations were compared with ethanol 70% and were traced throughout the period of 5 min. The results were obtained rapidly, frequently in less than 10 min. In conclusion, the effectiveness of a particular antibacterial disinfectant preparation may be estimated quantitatively within a few minutes by the flow cytometry. The method proved to be very useful for a fast comparison of the effectiveness of various disinfectant preparation against pathological microorganisms.