Cold Atmospheric Air Plasma Sterilization against Spores and Other Microorganisms of Clinical Interest

Klämpfl, Tobias G.; Isbary, Georg; Shimizu, Tetsuji; Li, Yang‐Fang; Zimmermann, Julia L.; Stolz, Wilhelm; Schlegel, Jürgen; Morfill, Gregor; Schmidt, Hans-Ulrich

doi:10.1128/aem.00583-12

Cited by 322 publications

(225 citation statements)

References 37 publications

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“…All experiments used the same parameters. The power density of the plasma discharge at the parameters noted above is estimated at ϳ35 mW/cm 2 (15). Exposure time was varied from 0 to 30 min, as stated below for each experiment, and the distance between the two electrodes was kept constant at 1.5 mm.…”

Section: Methodsmentioning

confidence: 99%

“…The optical emission spectrum of the SMD plasma was measured with a spectrometer (TRIAX 320; Horiba Scientific, Edison, NJ) and is shown in Fig. S1a in the supplemental material; it shows the presence of primarily UV-A light (315 to 400 nm) and almost no UV-C (200 to 280 nm) or UV-B (280 to 315 nm) light (15). The optical absorbance spectra of materials used to shield spores during plasma discharge were measured with a UV-visible (UV-Vis) spectrophotometer (GENESYS 10S; Thermo Fisher Scientific, Waltham, MA).…”

Section: Methodsmentioning

confidence: 99%

“…are typically reduced 4 to 6 logs by several minutes of treatment by different types of plasma systems (15)(16)(17)(18)(19)(20)(21)(22). The mechanisms of spore killing by plasma are complex (18), as UV photons, charged particles, electric fields, and reactive oxygen species (ROS) (e.g., ozone, atomic oxygen, and hydroxyl radicals if water is present) are all involved in spore killing (16,17).…”

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confidence: 99%

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Use of Raman Spectroscopy and Phase-Contrast Microscopy To Characterize Cold Atmospheric Plasma Inactivation of Individual Bacterial Spores

Wang

Doona

Setlow

et al. 2016

Appl Environ Microbiol

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Raman spectroscopy and phase-contrast microscopy were used to examine calcium dipicolinate (CaDPA) levels and rates of nutrient and nonnutrient germination of multiple individual Bacillus subtilis spores treated with cold atmospheric plasma (CAP). Major results for this work include the following: (i) >5 logs of spores deposited on glass surfaces were inactivated by CAP treatment for 3 min, while deposited spores placed inside an impermeable plastic bag were inactivated only ϳ2 logs in 30 min; (ii) >80% of the spores treated for 1 to 3 min with CAP were nonculturable and retained CaDPA in their core, while >95% of spores treated with CAP for 5 to 10 min lost all CaDPA; (iii) Raman measurements of individual CAP-treated spores without CaDPA showed differences from spores that germinated with L-valine in terms of nucleic acids, lipids, and proteins; and (iv) 1 to 2 min of CAP treatment killed 99% of spores, but these spores still germinated with nutrients or exogenous CaDPA, albeit more slowly and to a lesser extent than untreated spores, while spores CAP treated for >3 min that retained CaDPA did not germinate via nutrients or CaDPA. However, even after 1 to 3 min of CAP treatment, spores germinated normally with dodecylamine. These results suggest that exposure to the present CAP configuration severely damages a spore's inner membrane and key germination proteins, such that the treated spores either lose CaDPA or can neither initiate nor complete germination with nutrients or CaDPA. Analysis of the various CAP components indicated that UV photons contributed minimally to spore inactivation, while charged particles and reactive oxygen species contributed significantly. IMPORTANCEMuch research has shown that cold atmospheric plasma (CAP) is a promising tool for the inactivation of spores in the medical and food industries. However, knowledge about the effects of plasma treatment on spore properties is limited, especially at the single-cell level. In this study, Raman spectroscopy and phase-contrast microscopy were used to analyze CaDPA levels and kinetics of nutrient-and non-nutrient-germinant-induced germination of multiple individual spores of Bacillus subtilis that were treated by a planar CAP device. The roles of different plasma species involved in spore inactivation were also investigated. The knowledge obtained in this study will aid in understanding the mechanism(s) of spore inactivation by CAP and potentially facilitate the development of more effective and efficient plasma sterilization techniques in various applications.A mong low-temperature and nontoxic methods for microorganism inactivation, the application of cold atmospheric plasma (CAP) created by electrical discharge in a gas has attracted significant interest (1-5). CAP is a weakly ionized gas with a roughly zero net electrical charge and usually operates under atmospheric conditions below 40°C, with variations depending on the type of feed gas and the equipment configuration (6). Compared to conventional sterilization methods, such as w...

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Use of Raman Spectroscopy and Phase-Contrast Microscopy To Characterize Cold Atmospheric Plasma Inactivation of Individual Bacterial Spores

Wang

Doona

Setlow

et al. 2016

Appl Environ Microbiol

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“…ACP provides inactivation effects against a wide range of microbes, mainly by the generation of cell-lethal reactive species (6)(7)(8). By discharging in air, groups of reactive species are generated, such as reactive oxygen species (ROS), reactive nitrogen species (RNS), UV radiation, energetic ions, and charged particles (5).…”

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confidence: 99%

Mechanisms of Inactivation by High-Voltage Atmospheric Cold Plasma Differ for Escherichia coli and Staphylococcus aureus

Han¹,

Patil²,

Boehm³

et al. 2016

Appl Environ Microbiol

341

200

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bAtmospheric cold plasma (ACP) is a promising nonthermal technology effective against a wide range of pathogenic microorganisms. Reactive oxygen species (ROS) play a crucial inactivation role when air or other oxygen-containing gases are used. With strong oxidative stress, cells can be damaged by lipid peroxidation, enzyme inactivation, and DNA cleavage. Identification of ROS and an understanding of their role are important for advancing ACP applications for a range of complex microbiological issues. In this study, the inactivation efficacy of in-package high-voltage (80 kV [root mean square]) ACP (HVACP) and the role of intracellular ROS were investigated. Two mechanisms of inactivation were observed in which reactive species were found to either react primarily with the cell envelope or damage intracellular components. Escherichia coli was inactivated mainly by cell leakage and low-level DNA damage. Conversely, Staphylococcus aureus was mainly inactivated by intracellular damage, with significantly higher levels of intracellular ROS observed and little envelope damage. However, for both bacteria studied, increasing treatment time had a positive effect on the intracellular ROS levels generated.A tmospheric cold plasma (ACP) refers to nonequilibrated plasma generated at near-ambient temperatures and pressure. ACP is composed of particles, including free electrons, radicals, and positive and negative ions, but it is low in collision frequency of gas discharge compared to that with equilibrated plasma (1, 2). ACP technologies have widely been applied for many surface treatments and environmental processes. Recently, they have been studied for food sterilization and plasma medicine (2-5).ACP provides inactivation effects against a wide range of microbes, mainly by the generation of cell-lethal reactive species (6-8). By discharging in air, groups of reactive species are generated, such as reactive oxygen species (ROS), reactive nitrogen species (RNS), UV radiation, energetic ions, and charged particles (5). However, the inactivation efficacy can be varied by changing the working gases, which results in different types or amounts of reactive species generated (9-11). ROS are often identified as the principal effecting species, with a relatively long half-life and strong antimicrobial effects, which are generated in oxygen-containing gases (12).ROS generated during plasma discharge in air or oxygen-containing mixtures are assemblies of ozone, hydrogen peroxide, and singlet and atomic oxygen, while ozone is considered the most microbicidal species (13). With strong oxidative stress, cells are damaged by lipid peroxidation, enzyme inactivation, and DNA cleavage. The generation of plasma in air or a nitrogen-containing gas mixture can also generate NO x species. However, higher inactivation efficacy has been reported with the combined application of NO and H 2 O 2 on Escherichia coli than that with a treatment with NO or H 2 O 2 alone (14). Reactive nitrogen species are highly toxic and can lead to cell death by increas...

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“…In addition, I have published ISO-relevant books and papers, so based on these experiences I have prepared this article describing the application of ISO requirements to gas plasma sterilization. Gas plasma sterilization is a useful procedure that can easily achieve a sterility assurance level (SAL) of 10 -6 and material/ functional compatibility simultaneously [1][2][3][4][5] This is because the gas plasma penetration depth is quite shallow (10-20 nm) [1,2], so material does not deteriorate as easily compared with existing sterilization procedures. Current sterilization validation requires a SAL of 10 -6 and simultaneous material/functional compatibility.…”

mentioning

confidence: 99%

Sterilization Validation of Gas Plasma Exposure Based on ISO Documents(Mainly ISO TC 198 And 194 Documents)

Shintani¹

2015

Pharmaceut Reg Affairs

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There are so many ISO documents to understand and utilize for validation studies and routine control. A biological indicator (BI) is essential for conducting sterilization validation and routine control. ISO 11138-1 and ISO 14161 are the major documents to follow for BI manufacturers and BI users, respectively. In ISO 11138-1, BI manufacturers must utilize a BI with 10 6 CFU/carrier as an initial population for validation studies. For routine control, it is approved to use an initial BI population of 10 5 CFU/carrier according to ISO 11138-1. In ISO 14161 BI users need not imitate BI manufacturers and less than 10 6 CFU/carrier BI is approved for use in validation studies and routine control. According to ISO 14161 for BI users, the initial population must be identical for validation studies and routine control. For the BI user, there are four types of procedures for sterilization validation and routine control. These are the half-cycle, over-kill, combined BI/bioburden and the absolute bioburden methods. A BI with An initial population of 10 6 CFU/ carrier must be used for validation studies by BI manufacturers according to ISO 11138-1, but BI users can elect to use a commercially available BI with more than 10 3 CFU/carrier as the BI for validation studies and routine control as described in ISO 14161. The approved SAL was defined to be 10 -6 and this is unchanged for both BI users and BI manufacturers. Therefore, from the initial population of 10 6 CFU (colony forming unit)/carrier to a SAL of 10 -6 , the survivor curve must be straight and tailing is not allowed as described below (ISO 11138-1). The BI used for gas plasma sterilization, spores of Geobacillus stearothermophilus ATCC 7953, has characteristics that do not result in a tailing phenomenon. A linear survival curve is obtained from an initial population of 10 6 CFU/carrier to a SAL 10 -6 for all sterilization procedures tested, demonstrating that inactivation kinetics are first order and allowing calculation of the D (decimal reduction) value from the dose or time to decrease 1 log. Chemical indicators (CI) are not approved for use in validation studies; only the use of BI is approved. CIs are only approved for use as a supporting method during routine control according to ISO 11140-1 and 14161. Only a BI is approved for both validation studies and routine control according to ISO 14161. ISO documentsI am a Japan delegate of the ISO Technical Committee (TC) 198 and 194. TC 198 covers Sterilization of healthcare products. TC 194 covers Biological and clinical evaluation of medical devices. There are currently no ISO documents covering gas plasma sterilization. I have extensive experience in both the gas plasma sterilization field and as an ISO TC delegate. In addition, I have published ISO-relevant books and papers, so based on these experiences I have prepared this article describing the application of ISO requirements to gas plasma sterilization. Gas plasma sterilization is a useful procedure that can easily achieve a sterility assurance le...

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Cold Atmospheric Air Plasma Sterilization against Spores and Other Microorganisms of Clinical Interest

Cited by 322 publications

References 37 publications

Use of Raman Spectroscopy and Phase-Contrast Microscopy To Characterize Cold Atmospheric Plasma Inactivation of Individual Bacterial Spores

Use of Raman Spectroscopy and Phase-Contrast Microscopy To Characterize Cold Atmospheric Plasma Inactivation of Individual Bacterial Spores

Mechanisms of Inactivation by High-Voltage Atmospheric Cold Plasma Differ for Escherichia coli and Staphylococcus aureus

Sterilization Validation of Gas Plasma Exposure Based on ISO Documents(Mainly ISO TC 198 And 194 Documents)

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