Abstract/Summary

Salmonella is an important foodborne pathogen whose ability to resist stress and survive can vary between strains. This variability is normally not taken into account when predictions are made about survival in foods with negative consequences. Therefore, we examined the contribution of variable phenotypic properties to survival under stress in 10 Salmonella serovars. One strain (S. Typhimurium 10) was intentionally an RpoS-negative however, another one (S. Heidelberg) showed an rpoS mutation rendering it inactive. We assessed an array of characteristics (motility, biofilm formation, bile resistance, acid resistance and colony morphology) showing a major variability between strains associated with a 10- to 19-fold difference between the highest and the lowest strain for most characteristics. The RpoS status of isolates did not affect variability in the characteristics with the exception of resistance to NaCl, acetic acid, lactic acid, and the combination of acetic acid and salt where the variability between the highest and the lowest strain was reduced to 3.1-fold, 1.7-fold, 2-fold and 1.7-fold respectively, showing that variability was significant among RpoS-positive strains. Furthermore, we also found a good correlation between acid resistance and lysine decarboxylase activity showing its importance for acid resistance and demonstrated a possible role of RpoS in the lysine decarboxylase activity in Salmonella.