The Stability of rRNA in Heat-killed Salmonella enterica Cells and Its Detection by Fluorescent In Situ Hybridisation (FISH).

Differentiation of viable cells from non-viable cells is a major concern in the detection of foodborne microbial pathogens. Fluorescent in situ hybridisation (FISH) has been utilised as a promising method in this regard. The ability of FISH to differentiate viable cells from non-viable cells depends on the rapid degradation of rRNA in non-viable cells. In our work, Salmonella enterica that were heat-killed at 80°C, 100°C and 121°C were examined for the presence of rRNA using FISH at various times ranging from 5 minutes to 48 hours after heat treatment. rRNA was detected by FISH in heat-killed bacteria for 12 hours, 3 hours and 1 hour after treatment at 80°C, 100°C and 121°C, respectively. These results indicate that there is a correlation between temperature and stability of rRNA in heat-killed bacteria. In conclusion, FISH was determined to be a suitable method for differentiation of viable cells from non-viable cells, especially for samples subjected to extreme heat.