Aims: To examine the effect of temperature on the antimicrobial efficacy of lactate and propionate against O157 and non-O157 Escherichia coli isolates.
Methods and results: Lactate and, to a lesser extent, propionate effectively reduced viability at 37 degrees C. Ethanol enhanced this effect. Reducing the temperature to 20 or 5 degrees C caused an increase in survival in the presence of these organic acids with or without ethanol. At 20 degrees C the deltapH, membrane potential and intracellular lactate anion concentration were less than at 37 degrees C.
Conclusions: The efficacy of lactate and propionate against E. coli O157 and non-O157 isolates is reduced at lower temperatures, perhaps due to the reduction in the deltapH, membrane potential and intracellular lactate anion concentration.
Significance and impact of the study: These findings suggest that the usefulness of organic acids as decontaminants for E. coli O157 is temperature dependent.