Susceptibility of Escherichia coli O157 and non-O157 isolates to lactate

To examine the effect of temperature on the antimicrobial efficacy of lactate and propionate against O157 and non-O157 Escherichia coli isolates.

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.

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.

These findings suggest that the usefulness of organic acids as decontaminants for E. coli O157 is temperature dependent.