Resistance of Enterobacter sakazakii (Cronobacter spp.) to environmental stresses

Aim: To gain a better understanding of the survival and persistence of Enterobacter sakazakii in severe environments. Methods and Results: We evaluated the resistance of Ent. sakazakii to various environmental stresses, including heating, drying, water activity (a_w), and pH. The resistance of Ent. sakazakii to heat varies widely among strains. Most tested strains of Ent. sakazakii exhibited unusual resistance to dry stress, which depends on drying media. Growth of most strains occurred within 24 h at 37°C when the initial a_w of the medium was adjusted to 0·94 with sucrose or sodium chloride. The minimum pH for growth within 24 h at 37°C was 3·9 or 4·1 for most strains tested. Additionally, there did not appear to be any relationship between resistance to stresses and biofilm-forming ability in Ent. sakazakii planktonic cells. Conclusions: These results indicate that Ent. sakazakii is much more resistant than other Enterobacteriaceae to environmental stresses. Moreover, it is likely that Ent. sakazakii has cross-resistance to dry and thermal stresses. Significance and Impact of the Study: The findings of this study will contribute to an improved understanding of the survival and behaviour of Ent. sakazakii, which will lead to improved strategies for preventing outbreaks of Ent. sakazakii infection.