We study the sensibility of Salmonella enterica serovar Enteritidis strain to several treatments that are very similar to the intracellular environment they used to find when are phagocyted. So, the treatments used were : incubation with H202, starving, long stationary phase, acid pH, and methyl methane sulfonate (MMS). To detect cell viability we used two fluorochromes Rh123 and PI that detect a loss of selective permeability and low cell activity. We try to compare the traditional colony counting with percentage of viability.

To do this we used Bryte-HS (Bio-Rad) flow cytometer. This machine is able to give absolute counting and two fluorescences. Its sensibility is higher than other instruments and allows differentiate several populations by size and granularity.

The results obtained show that the new method is more sensible, faster and easier than colony counting method (3 hours for the first one and two days for the second, the machine gives you the number directly in the first one and in the second you have to waste several hours counting colonies.

On the other hand, first results obtained with the new method show that Salmonella enterica serovar Enteritidis is very sensible to H202 treatment (90% death cells after 3 hours of treatment), and is less sensible to acid pH (60% death cell after 3 hours).