Effect of Ethanol Shock Pretreatment on the Tolerance ofCronobacter sakazakiiBCRC 13988 Exposed to Subsequent Lethal Stresses

Cronobacter spp., formerly Enterobacter sakazakii, are human pathogens. They are the etiological agent of life-threating bacterial infections in infants. In this study, the survival behavior of C. sakazakii Bioresources Collection and Research Center (BCRC) 13988 in the presence of various ethanol concentrations was first examined. Besides, the test organism was subjected to treatment with 5% ethanol for 60 min (ethanol shock). The effect of ethanol shock on the resistance of C. sakazakii to lethal stresses, including high ethanol concentration (15%), low temperature (4°C and -20°C), high temperature (51°C) and high acidity (pH 3.3), was investigated. Results revealed that 4-5% ethanol is the maximum concentration that will allow C. sakazakii BCRC 13988 to grow in trypticase soy broth (TSB). Etthanol at 6% and 7% or more, respectively, exerted bacteriostatic and bactericidal effects, respectively, on the test organism. Although ethanol shock did not affect the resistance of C. sakazakii to a refrigerated temperature (4°C), the ethanol-shocked C. sakazakii survived better under other lethal stress conditions. After 50 min of exposure to 15% ethanol, the ethanol-shocked C. sakazakii showed a survival percentage of 16.11%, which was a 6400-fold increase over the control cells (