Synergistic effect of microwave heating and hydrogen peroxide on inactivation of microorganisms.

Escherichia coli K-12 isogenous strains and Pseudomonas aeruginosa 102 were used to study the synergistic effects of combined microwave heating at short-time processing with low concentrations of hydrogen peroxide. The effect of microwave heating to temperatures of 40, 50 and 60 degrees C, as well as the concentration of hydrogen peroxide (0.05, 0.08 and 0.1%), the sequence of the agents' use, the nature of microorganisms on the survival of cells, DNA damages and interaction factors were studied. A method of anomalous viscosity time dependencies (AVTD) was used for measurement of the changes of genome conformational state (GCS) simultaneously with bacterial survival determination. The synergistic effect of microwave heating and low concentrations of hydrogen peroxide was observed under combined application, and reached a maximum when the cells were exposed to microwave heating to 50 degrees C and 0.08% hydrogen peroxide simultaneously. Both maxima of cell destruction and DNA injuries have been achieved by successive exposure to (MW + 10 min H2O2) to 60 degrees C and 0.08% hydrogen peroxide. The mechanisms of synergistic effects, the role of a disturbance of DNA repair and the interaction of sublethal injuries caused by different agents are discussed.

Modification of bactericidal effects of microwave heating and hyperthermia by hydrogen peroxide.

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 isogenous strains of Escherichia coli K-12 to microwave heating and hyperthermia with the following assessment of their combined action. This was carried out simulataneously and successively under equal conditions of temperature rise at 50 degrees 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 hyperthermia and microwave heating over a range of temperatures from 40 to 80 degrees 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. coli AB 1157 cells was determined. It was shown by the AVTD method that microwave heating at a temperature increase of 6 degrees 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 simulataneous 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.

[Mechanisms of the combined effect of SHF electromagnetic radiation and hydrogen peroxide on the viability of microorganisms]. / Issledovanie mekhanizmov kombinirovannogo deistviia élektromagnitnogo izlucheniia SVCh i perekisi vodoroda na zhiznesposobnost' mikroorganizmov.

The cellular (viability) and molecular (kinetics of changes in nucleoid viscosity) mechanisms of damage to various strains of microorganisms after single and combined action of SHF electromagnetic radiation and hydrogen peroxide are compared. The conditions are found in which marked synergetic interactions of the agents are realized. The role of repair systems in formation of final products of the interactions is discussed.

[Comparative analysis of mechanisms of the modification of microorganism viability under the effect of UHF heating and hyperthermia]. / Sravnitel'nyi analiz mekhanizmov modifikatsii zhiznesposobnosti mikroorganizmov pri vozdeistvii SVCh-nagreva i gipertermii.

In experiments with models of isogenic Escherichia coli strains, a comparative study was made of the effect of SHF of electromagnetic field and hyperthermia. The survival rate of bacteria was determined and, simultaneously, injuries to genetic supramolecular structures were registered through measuring the anomalous time dependence of cell lysate viscosity. The combined effects of the mixture of these factors with H2O2 microconcentrations were studied. The differences observed in their realization were attributed to the different mechanisms of action of these factors on the repair enzyme systems of the studied cells. It has been found that the effect of microwaves on microorganisms causes much severer damages to DNA that hyperthermia does.

[The combined action of microwave radiation and hydrogen peroxide on the viability and ultrastructure of Pseudomonas aeruginosa cells]. / Sochetannoe deistvie mikrovolnovogo izlucheniia i perekisi vodoroda na zhiznesposobnost' i ul'trastruktury kletok Pseudomonas aeruginosa.

The comparative study of the action of microwave radiation and hydrogen peroxide, as well as their combined action, on the viability and ultrastructure of P. aeruginosa cells has been made. The combined use of microwave radiation and hydrogen peroxide has been shown to decrease the viability of P. aeruginosa 1.5-2 times in comparison with the isolated action of each factor. The electron microscopic study of the ultrastructure of cells have shown the deterioration of the surface structures, nuclear and ribosomal apparatus of the cells under the isolated action of each of the above-mentioned factors or under their combined action. The morphological picture of these changes has proved to be different. The maximum changes in the ultrastructure of P. aeruginosa cells have been registered after the combined action of these bactericidal factors.