Abstract
Cronobacter sakazakii, formerly Enterobacter sakazakii, has been implicated in a severe form of neonatal meningitis. In this study, C. sakazakii BCRC 13988 was first exposed to heat-shock treatment at 47°C for 15 min. The heat-shocked C. sakazakii was subjected to several lethal challenges including low temperature (3°C and −20°C), pH 3.3, 15% ethanol, high osmotic pressure (tryptic soy broth + 75% sorbitol, a w 0.81), and drying. It was found that heat shock significantly (p < 0.05) enhanced the resistance of C. sakazakii to all the lethal stresses examined. After 60 min of exposure to 15% ethanol, the survival of the heat-shocked cells was ∼752 times that of the nonshocked cells. Compared with the nonshocked C. sakazakii, the heat-shocked cells exhibited a 322- and 1.6-fold increase in survival after 7 days of exposure to −20°C and 3°C, respectively. A 48-fold increase in the survival was noted with the heat-shocked cells after 6 h of exposure to dry air (relative humidity 37%) at 25°C, showing a survival of 0.00107% which is ∼50-fold that of the control. After 36 h of exposure to the high osmotic stress environment, the survival of the heat-shocked C. sakazakii was found to be ∼119 times that of the control cells. Finally, an increased survival of ∼72 times that of the control cells was observed with the heat-shocked C. sakazakii after 60 min of challenge at pH 3.3.
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