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Aims: In case of biological hazards and pandemics, personal protective equipment of rescue forces is currently manually decontaminated with harmful disinfectants, primarily peracetic acid. To overcome current drawbacks regarding supply, handling and disposal of chemicals, the use of plasma processed air (PPA) represents a promising alternative for surface decontamination on site. In this study, the sporicidal efficiency of a portable plasma system, designed for field applications, was evaluated. Methods and Results: The developed plasma device is based on a dielectric barrier discharge (DBD) and operated with ambient air as process gas. PPA from the plasma nozzle was flushed into a treatment chamber (volume: 300 l) and bacterial endospores (Bacillus subtilis and Bacillus atrophaeus) dried on different surfaces were treated under variable conditions. Reductions in spores by more than 4 log10 were found within 3 min of PPA exposure. However, the presence of endospores in agglomerates or in an organic matrix as well as the complexity of the respective surface microstructure negatively affected the inactivation efficiency. When endospores were embedded in a dried protein matrix, mechanical wiping with swabs during exposure to PPA increased the inactivation effect significantly. Gaseous ozone alone did not provide a sporicidal effect. Significant spore inactivation was only obtained when water vapour was injected into the PPA stream. Conclusion: The results show that endospores dried on surfaces can be reduced by several orders of magnitude within few minutes in a treatment chamber which is flushed with PPA from of a DBD plasma nozzle. Significance and Impact of the Study: Plasma processed air generated on site by DBD plasma nozzles could be a suitable alternative for the disinfection of various surfaces in closed rooms. [ABSTRACT FROM AUTHOR]

To investigate the effect of a cascaded dielectric barrier discharge (CDBD) treatment on the biological structure of a selected bacterium and on the properties of different polymer films. Inactivation kinetics were measured using air as the process gas and using Bacillus atrophaeus spores and vegetative cells, which had been homogeneously distributed on a surface. The changes to the outer coats and the DNA of the endospores and cells after plasma treatment were determined using biomolecular and chemical methods. The experiments showed that damage to the DNA molecules and changes in the cell walls can be observed as a consequence of the CDBD treatment. Furthermore, the influence of the plasma treatment on the properties of various polymer films was investigated using a variety of test methods. Except the sealing strength where a slight decrease was observed (max. 20%), no negative changes of the material properties have occurred. CDBD treatment can affect the DNA of spores and cells, depending on the treatment time. At the same time, practically relevant inactivation rates on packaging materials were observed, without any significant changes to the material properties. Knowledge about CDBD mechanisms was acquired from a biological point of view, and the suitability of the method for treating polymer films was demonstrated. [ABSTRACT FROM AUTHOR]

The impact of the fluence regulation on the inactivation efficiency of pulsed light (PL) surface disinfection treatments was investigated. E. coli and L. innocua were exposed to PL on a gel surface under variation of the applied voltage, the number of light flashes as well as the distance between the flash lamp and the sample surface. The results revealed deviations from the reciprocity law when the total fluence striking the sample surface was not applied at once, but subdivided into several successive light flashes. No differences were found when the fluence was delivered with only single light flashes, irrespective of the applied voltage. The pulse frequency did not have an impact on the microbial reduction within 1–5 Hz. Furthermore, the sensitivities of various bacterial strains, endospores and conidiospores were compared. Differences occurred for vegetative bacteria without a clear pattern, while bacterial endospores were more resistant. Dark pigmented mold spores were slightly more resistant than bacterial endospores. All dose-response curves exhibited a downward concavity, except for P. aeruginosa . Industrial relevance This study shows that the inactivation of bacteria on e.g. food surfaces by pulsed light systems depends on the way of fluence dosage. While it is irrelevant whether the fluence is regulated by the discharge voltage or the distance between the flash lamp and the treated surface, it is more effective to apply only single light flashes of high fluence instead of several consecutive light flashes. There is furthermore no distinct trend regarding the sensitivity of bacteria to PL, variations occur on species and strain level. Bacterial spores are in general more resistant while pigmented conidiospores show a slightly higher resistance than bacterial endospores. [ABSTRACT FROM AUTHOR]