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Interaction of non-thermal plasma at atmospheric pressure (CAPP) with non-pathogenic bacteria
Chobotská, Barbora ; Brázda, Václav (referee) ; Kozáková, Zdenka (advisor)
The subject of this bachelor thesis is the study of decontamination effects of cold atmospheric pressure plasma (CAP) on selected bacteria Escherichia coli and Staphylococcus epidermidis. A non-thermal microwave plasma torch was used. The plasma torch was connected to the software in the computer, which allowed its movement over the treated area. The used power fluctuated between 12–13 W and argon (gas purity 4.6) was chosen as the working gas with a constant flow rate of 5 l/min Inhibition efficacy was observed depending on the type of the selected treatment. The chosen treatment parameters included the effect of speed, direction, and treatment time for both studied bacteria. The aim was to achieve the highest decontamination of the treated area and to determine which of these parameters appeared to be the most significant. No obvious difference (between the treatment directions) was found in the overall decontamination of the treated area for studied bacteria Escherichia coli. The negative effect of speed was only observed for the fastest speed used in the case of gram-positive Staphylococcus epidermidis. The most significant parameter was found to be the treatment time, where a significant decrease in colony growth was observed with increasing treatment time. Furthermore, a repeated treatment was done, where the inoculum was prepared from the already treated bacteria. By this set of experiments, possible development of microbial resistance against the plasma treatment was tested. The results showed that there was no significant increase in the number of colonies even after the repeated treatment. It was also observed that the gram-positive bacteria Staphylococcus epidermidis showed lower decontamination effect evaluated via the number of colonies than the gram-negative bacteria Escherichia coli for all treatment types studied.

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