Modification of Bactericidal Effects of Microwave Heating and Hyperthermia by Hydrogen Peroxide

Abstract

Two different approaches for studying of bactericidal effects of microwave heating and hyperthermia were introduced. Low concentration of hydrogen peroxide (0.05%) was used to modify the sensitivity of isogerwus strains of Escherichia coli K-12 to microwave heating and hyperthernzia with the following assessment of their combined action. This was carried out simultaneously and successively under equal conditions of temperature rise at 50°C. A method of anomalous viscosity time dependencies (AVTD) was used for measurement of the changes in genome conformational state simultaneously with bacterial survival determination. Experiments were performed to study isolated effects of hyper-the rmia and microwave heating over a range of temperatures from 40 to 80° C and hydrogen peroxide concentrations from 0.05 to 0.3% during 10-minute exposures and their combined action. No difference was found between isolated effects of microwave heating and hyperthermia when survival of E. co li AB 1157 cells was determined. It was shown by the AVTD method that microwave heating at a temperature increase of 6° C per second caused greater damage to cell genome than hyperthermia. The synergistic interaction of microwave heating and low concentrations of hydrogen peroxide was found in simultaneous and successive exposures. The essential distinctions observed in recognition of the action of microwave heating and hyperthermia combined with hydrogen peroxide in various sequences on cellular and molecular levels were attributed to the different effects of microwave and conventional heating on the systems of DNA repair.