Sodium chloride enhances recovery and growth of acid-stressed E. coli O157:H7

Abstract

Aims: Combinations of sodium chloride and acid are frequently used to inhibit growth of spoilage and pathogenic bacteria in food. The influence of differing sodium chloride, lactate and pH values on the growth of stressed and unstressed cells of a non-toxigenic strain of Escherichia coli O157:H7 was studied.

Methods and results: At pH 5.5 or 6.0, there was little or no effect on the growth rate in the presence of lactate and/or sodium chloride, but the lag times were longer as the lactate concentration increased. At pH 5.0, in the absence of sodium chloride, increasing the lactate concentration increased the growth rate and the lag time; no growth occurred in the presence of 1.5 g 100 g(-1) lactate. In the presence of 4-6 g 100 g(-1) sodium chloride, growth occurred at 1.5 g 100 g(-1) lactate. The growth rate was similar at all lactate concentrations.

Conclusion: The results demonstrate that the presence of sodium chloride promoted growth of E. coli O157:H7, especially under stressful conditions of low pH.

Significance and impact of the study: These findings could have implications for the use of acid and sodium chloride as a preservation treatment for the inhibition of E. coli O157:H7 in food.