Cold atmospheric air plasma sterilization against spores and other microorganisms of clinical interest
Tobias G Klämpfl1, Georg Isbary, Tetsuji Shimizu
1Max Planck Institute for Extraterrestrial Physics, Garching, Germany. klaempfl@mpe.mpg.de
Abstract:
Physical cold atmospheric surface microdischarge (SMD) plasma operating in ambient air has promising properties for the sterilization of sensitive medical devices where conventional methods are not applicable. Furthermore, SMD plasma could revolutionize the field of disinfection at health care facilities. The antimicrobial effects on Gram-negative and Gram-positive bacteria of clinical relevance, as well as the fungus Candida albicans, were tested. Thirty seconds of plasma treatment led to a 4 to 6 log(10) CFU reduction on agar plates. C. albicans was the hardest to inactivate. The sterilizing effect on standard bioindicators (bacterial endospores) was evaluated on dry test specimens that were wrapped in Tyvek coupons. The experimental D(23)(°)(C) values for Bacillus subtilis, Bacillus pumilus, Bacillus atrophaeus, and Geobacillus stearothermophilus were determined as 0.3 min, 0.5 min, 0.6 min, and 0.9 min, respectively. These decimal reduction times (D values) are distinctly lower than D values obtained with other reference methods. Importantly, the high inactivation rate was independent of the material of the test specimen. Possible inactivation mechanisms for relevant microorganisms are briefly discussed, emphasizing the important role of neutral reactive plasma species and pointing to recent diagnostic methods that will contribute to a better understanding of the strong biocidal effect of SMD air plasma.
Insights
Surface microdischarge plasma offers rapid sterilization for medical devices and healthcare disinfection. This cold atmospheric plasma effectively inactivates bacteria and fungi, showing promise for sensitive materials.
Area of Science:
- Microbiology
- Plasma Physics
- Biophysics
Background:
- Conventional sterilization methods are unsuitable for many sensitive medical devices.
- Surface microdischarge (SMD) plasma in ambient air presents a novel disinfection approach.
- SMD plasma has potential applications in healthcare settings for enhanced disinfection.
Purpose of the Study:
- To evaluate the antimicrobial efficacy of SMD plasma against clinically relevant microorganisms.
- To determine the sterilizing effect of SMD plasma on bacterial endospores.
- To investigate the inactivation mechanisms of SMD plasma.
Main Methods:
- Testing antimicrobial effects on Gram-negative bacteria, Gram-positive bacteria, and Candida albicans.
- Evaluating sterilization on bioindicators (bacterial endospores) using Tyvek coupons.
- Determining decimal reduction times (D values) at 23°C for various bacterial species.
Main Results:
- Thirty seconds of SMD plasma treatment achieved a 4 to 6 log(10) CFU reduction for bacteria and fungi.
- Candida albicans demonstrated higher resistance to inactivation compared to bacteria.
- Determined low D values for Bacillus subtilis, Bacillus pumilus, Bacillus atrophaeus, and Geobacillus stearothermophilus, indicating high efficacy.
- Inactivation rates were independent of the test specimen material.
Conclusions:
- SMD plasma exhibits potent antimicrobial activity against a range of microorganisms.
- The low D values suggest SMD plasma is a highly effective sterilizing agent.
- Neutral reactive plasma species play a crucial role in the biocidal effects of SMD air plasma.
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