Atmospheric pressure, nonthermal plasma inactivation of MS2 bacteriophage: effect of oxygen concentration on virucidal activity

AimsThe main aim of this study was to determine the virucidal inactivation efficacy of an in-house-designed atmospheric pressure, nonthermal plasma jet operated at varying helium/oxygen feed gas concentrations against MS2 bacteriophage, widely employed as a convenient surrogate for human norovirus.

Methods and ResultsThe effect of variation of percentage oxygen concentration in the helium (He) carrier gas was studied and found to positively correlate with MS2 inactivation rate, indicating a role for reactive oxygen species (ROS) in viral inactivation. The inactivation rate constant increased with increasing oxygen concentrations up to 075% O-2. 3 log(10) (999%) reductions in MS2 viability were achieved after 3min of exposure to the plasma source operated in a helium/oxygen (9925%:075%) gas mixture, with >7 log(10) reduction after 9min exposure.

ConclusionsAtmospheric pressure, nonthermal plasmas may have utility in the rapid disinfection of virally contaminated surfaces for infection control applications.

Significance and Impact of StudyThe atmospheric pressure, nonthermal plasma jet employed in this study exhibits rapid virucidal activity against a norovirus surrogate virus, the MS2 bacteriophage, which is superior to previously published inactivation rates for chemical disinfectants.

Tubular cathode prepared by a dip-coating method for low temperature DMFC

A novel tubular cathode for the direct methanol fuel cell (DMFC) is proposed, based on a tubular titanium mesh. A dip-coating method has been developed for its fabrication. The tubular cathode is composed of titanium mesh, a cathode diffusion layer, a catalyst layer, and a recast Nafion® film. The titanium mesh is present at the inner circumference of the diffusion layer, while the recast Nafion® film is at the outer circumference of the catalyst layer. A DMFC single cell with a 3.5 mgPt cm tubular cathode was able to perform as well, in terms of power density, as a conventional planar DMFC. A peak power density of 9 mW cm was reached under atmospheric air at 25 °C. © 2006 WILEY-VCH Verlag GmbH & Co. KGaA.

Potential Cellular Targets and Antibacterial Efficacy of Atmospheric Pressure Non-Thermal Plasma

Atmospheric pressure non-thermal plasma (APNTP) has been gaining increasing interest as a new alternative antibacterial approach. Although this approach has demonstrated promising antibacterial activity, its exact mechanism of action remains unclear. Mechanistic elucidation of the antimicrobial activity will facilitate development and rational optimisation of this approach for potential medical applications. In this study, the antibacterial efficacy of an in-house-built APNTP jet was evaluated alongside an investigation of the interactions between APNTP and major cellular components in order to identify the potential cellular targets involved in plasma-mediated bacterial destruction mechanisms. The investigated plasma jet exhibited excellent, rapid antibacterial activity against a selected panel of clinically significant bacterial species including Bacillus cereus, meticillin-resistant Staphylococcus aureus (MRSA), Escherichia coli and Pseudomonas aeruginosa, all of which were completely inactivated within 2 min of plasma exposure. Plasma-mediated damaging effects were observed, to varying degrees, on all of the investigated cellular components including DNA, a model protein enzyme, and lipid membrane integrity and permeability. The antibacterial efficacy of APNTP appears to involve a multiple-target mechanism, which potentially reduces the likelihood of emergence of microbial resistance towards this promising antimicrobial approach. However, cellular membrane damage and resulting permeability perturbation was found to be the most likely rate-determining step in this mechanism. Crown Copyright © 2013.

Microscopic Examination of Biofilm Destruction by Atmospheric Pressure Plasma

Objective: The aim of this study is to examine microscopically the destruction of bacterial biofilms mediated by atmospheric pressure non-thermal plasma (APNTP) at cellular level as well as at the level of biofilm structure as a whole. Methods: 3-day old bacterial biofilms were grown on polycarbonate coupons in a dual channel flow cell and were treated with an in-housed designed atmospheric pressure non-thermal plasma jet for up to 4 minutes of exposure before being examined by both confocal laser scanning microscopy (CLSM), preceded by Live/Dead bacterial viability staining, and scanning electron microscopy (SEM). Results: Differential live/dead staining followed by confocal microscopy examination revealed that biofilm eradication by APNTP was mediated by varying levels of both cell killing and physical removal. Relative extent of each mechanism was dependent on plasma operating conditions, bacterial species, growth conditions and biofilm thickness. On the other hand, SEM examination of plasma-exposed biofilms revealed a series of morphological changes exhibited by biofilm cells ranging from increased roughness of cell surface to complete cell lysis. Conclusions: Interesting mechanistic insights have been revealed by microscopic examination of plasma-treated bacterial biofilms that, when coupled with more specific biochemical studies, will not only contribute significantly to our understanding of the mechanism of plasma mediated biofilm destruction but also will help in better application-guided development of this novel anti-biofilm approach.