Potentiation of the lethal effect of peroxygen on Bacillus cereus spores by alkali and enzyme wash.

Bacillus cereus present in pipes and heat-exchangers represents a potential quality problem for dairy industry. The peroxygen-containing disinfectants investigated had only negligible sporicidal effect when applied at the recommended in-use temperature and concentration. However, cleaning agents used before disinfection potentiated their lethal activity. Pre-exposure of B. cereus spores to 1% sodium hydroxide at temperatures over 40 degrees C increased the sporicidal effect of the peroxygen-containing disinfectant. The effect was dependent on the alkali concentration and the temperature. Also, a significant potentiating activity of an enzyme-based cleaning agent was obtained, but the effect was smaller than for alkali treatment. The results indicated that disinfectants based on peroxygen can be used to eliminate B. cereus spores at non-corrosive temperatures and concentrations if the surfaces are cleaned with alkali or enzyme-based disinfectants prior to disinfection.