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

Abstract

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 radiodurans 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 min for its complete inactivation.

The Influence of Parameters of Stabilized Corona Discharge on its Microbicidal Effect

“…The efficiency of inactivation is slightly different for various bacterial species, but no dependence on the bacterial type (Gram-negative or Gram-positive) or shape (rod or coccus) can be concluded. This result accords with our previous studies of low-temperature plasma microbicidal effects [5]. In the same work we also reported that the yeast was the most sensitive microbe when deposited on the wet agar surface, whereas its inactivation in suspension needs several times longer exposition than bacterial suspensions.…”

“…The yeast deposited on the agar surface displays similar or better sensitivity to the corona discharge in comparison with bacteria [5]. 5.…”

“…The low temperature plasma was generated using the previously described [5,6] simple apparatus of an open--air type. Briefly, the negative or positive corona discharges were generated on the point electrode represented by the tip of a syringe needle, stabilized by the serial resistance of 20 MΩ connected between the source of DC high voltage and the plane electrode, realized by the surface of water suspension of microorganisms grounded * corresponding author; e-mail: scholtzv@vscht.cz with an immersed platinum wire.…”

Low temperature atmospheric pressure plasma sources for microbial decontamination

“…Usually, negative dc corona discharges are used for microbial inactivation although microbial inactivation has also been shown for different pulsed modes (Cramariuc et al, 2008). Scholtz et al (2010) studied the microbicidal effect of a negative DC corona in ambient air using a pin to plate geometry (see figure 2a). High voltages up to 10 kV and currents up to 0.5 mA were adjusted.…”

“…a) Plasma is generated at the point of the negative electrode. b) A thin plasma channel occurs between a pointed negative electrode and a grounded one due to a sufficient argon flow (according to Scholtz et al (2010) and Bussiahn et al (2010)). …”