Nonthermal Plasma Jet Treatment Negatively Affects the Viability and Structure of Candida albicans SC5314 Biofilms

Abstract

Microorganisms are predominantly organized in biofilms, where cells live in dense communities and are more resistant to external stresses than are their planktonic counterparts. With experiments, the susceptibility of biofilms to a nonthermal plasma treatment (plasma source, kINPen09) in terms of growth, survival, and cell viability was investigated. strain SC5314 (ATCC MYA-2876) was plasma treated for different time periods (30 s, 60 s, 120 s, 180 s, 300 s). The results of the experiments, encompassing CFU, fluorescence Live/Dead, and 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide salt (XTT) assays, revealed a negative influence of the plasma treatment on the proliferation ability, vitality, and metabolism of biofilms, respectively. Morphological analysis of plasma-treated biofilms using atomic force microscopy supported the indications for lethal plasma effects concomitant with membrane disruptions and the loss of intracellular fluid. Yielding controversial results compared to those of other publications, fluorescence and confocal laser scanning microscopic inspection of plasma-treated biofilms indicated that an inactivation of cells appeared mainly on the bottom of the biofilms. If this inactivation leads to a detachment of the biofilms from the overgrown surface, it might offer completely new approaches in the plasma treatment of biofilms. Because of plasma's biochemical-mechanical mode of action, resistance of microbial cells against plasma is unknown at this state of research. Microbial communities are an increasing problem in medicine but also in industry. Thus, an efficient and rapid removal of biofilms is becoming increasingly important. With the aid of the kINPen09, a radiofrequency plasma jet (RFPJ) instrument, decisive new findings on the effects of plasma on biofilms were obtained. This work showed that the inactivation of biofilms takes place mainly on the bottom, which in turn offers new possibilities for the removal of biofilms by other strategies, e.g., mechanical treatment. This result demonstrated that nonthermal atmospheric pressure plasma is well suited for biofilm decontamination.

Antimicrobial effects of microwave‐induced plasma torch (MiniMIP) treatment on Candida albicans biofilms

“…Consequently, PTW was generated at the bottom layers of the biofilm and predominantly led to an inactivation in that area. This was also indicated in treatments with the kINPen09 in the same experimental set‐up (Handorf, Weihe et al , ).…”

“…Indirect treatment of microorganisms where the effluent has been brought into a short distance over the biofilms is published for plasma jets or DBDs (Maisch, Shimizu et al , ; Khan, Lee et al , ; Handorf, Weihe et al , ). If only the achieved reduction factors are considered for the same treatment time regardless of the type of plasma generation and type of application, RFs of 0.6 for the kINPen09, 2.9 for the hollow electrode dielectric discharge (HDBD) and 2.3 for the volume dielectric discharge (VDBD) were obtained after 1 min treatment time (Koban, Matthes et al , ).…”

“…In terms of three‐dimensional effects, RFPJ treatments showed centralized spots of dead cells while the majority of biofilm cells were not affected by plasma treatment (Handorf, Weihe et al , ). This occurred mainly due to the relatively fine and centralized effluent of plasma jets.…”

“…In order to meet the industrial requirements, it is of particular importance to find standardized parameters for the plasma source. Despite antimicrobial effects of a different plasma source on C. albicans having been shown (Handorf, Weihe et al , ), no studies exist, which investigated the effects of the MiniMIP on C. albicans biofilms up to this date.…”

Characterization of Antimicrobial Effects of Plasma‑Treated Water (PTW) Produced by Microwave‑Induced Plasma (MidiPLexc) on <em>Pseudomonas fluorescens </em>Biofilms

“…The main priority is the complete detachment of the biofilm from the overgrown surface to remove it from the system during the flushing processes. Initial studies have already shown a unique effect of plasma gas on the adhering surface of the biofilm [28,29]. The present study aimed to investigate whether PTW also has such special effects on the biofilm.…”