The Microbicidal Effect of Low-Temperature Plasma Generated by Corona Discharge: Comparison of Various Microorganisms on an Agar Surface or in Aqueous Suspension

The sensitivity of various microbes to the low temperature plasma generated by negative corona discharge in the point-to-plane mode was tested. On the surface of agar semisolid cultivation media, the inhibition zones in microbial cultures were obtained and their areas were compared as a measure of microbicidal effect for nine microbial species including bacterial spores and a yeast species. This experimental arrangement resembles the testing of antibiotic sensitivity by the well-known disc diffusion technique. The effect of comparable magnitude was found for all vegetative forms, but Candida albicans and Deinococcus radio-durans appeared to be the most and Geobacillus stearothermophilus the least susceptible. The effect on spores was in order of magnitude lesser than on vegetative forms. Following the action of the same plasma on bacteria in aqueous suspensions, the complete sterilization of Escherichia coli was achieved within 120 s and Staphylococcus epidermidis within 4-5 min. On the other hand, the yeast Candida albicans in water appeared to be less susceptible requiring 30 mm for its complete inactivation.