Fate of Escherichia coli O157:H7 in coleslaw during storage

An outbreak of Escherichia coli O157:H7 infection associated with the consumption of coleslaw in several units of a restaurant chain prompted a study to determine the fate of the pathogen in two commercial coleslaw preparations (pH 4.3 and 4.5) held at 4, 11, and 21degreesC for 3 days. At an initial population of 5.3 log(10) CFU/g of coleslaw, E. coli O157:H7 did not grow in either coleslaw stored at the three temperatures. Rather, the population of E. coli O157:H7 decreased by 0.1 to 0.5 log(10) CFU/g within 3 days. The greatest reduction (0.4 and 0.5 log(10) CFU/g) in population occurred at 21degreesC, whereas only slight decreases (0.1 to 0.2 log(10) CFU/g) occurred at 4 and 11degreesC. A pH of 4.3 to 4.5 of coleslaw had little effect on reducing E. coli O157:H7 populations. Results suggest that the tolerance of E. coli O157:H7 to acid pH, not temperature abuse, is a major factor influencing the pathogen's fate in restaurant-prepared coleslaw.