Acid Stress, Starvation, and Cold Stress Affect Poststress Behavior of Escherichia coli O157:H7 and Nonpathogenic Escherichia coli†

Abstract

The effects of acid shock, acid adaptation, starvation, and cold stress of Escherichia coli O157:H7 (ATCC 43895), an rpo S mutant (FRIK 816-3), and nonpathogenic E. coli (ATCC 25922) on poststress heat resistance and freeze–thaw resistance were investigated. Following stress, heat tolerance at 56°C and freeze–thaw resistance at −20 to 21°C were determined. Heat and freeze–thaw resistance of E. coli O157:H7 and nonpathogenic E. coli was enhanced after acid adaptation and starvation. Following cold stress, heat resistance of E. coli O157:H7 and nonpathogenic E. coli was decreased, while freeze–thaw resistance was increased. Heat and freeze–thaw resistance of the rpoS mutant was enhanced only after acid adaptation. Increased or decreased tolerance of acid-adapted, starved, or cold-stressed E. coli O157:H7 cells to heat or freeze–thaw processes should be considered when processing minimally processed or extended shelf-life foods.