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DiNicola M, Seuylemezian A, Guan L, Moissl-Eichinger C, Baker A, Johns J. Modeling of recovery efficiency of sampling devices used in planetary protection bioburden estimation. Appl Environ Microbiol 2023; 89:e0083223. [PMID: 37982623 PMCID: PMC10734503 DOI: 10.1128/aem.00832-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Accepted: 09/22/2023] [Indexed: 11/21/2023] Open
Abstract
IMPORTANCE Planetary protection at the National Aeronautics and Space Administration (NASA) requires bioburden on certain spacecraft to be estimated via sampling in order to comply with biological cleanliness requirements. To achieve this, the recovery efficiency of devices used to sample the spacecraft pre-launch must be understood and their uncertainty quantified in order to produce the most reasonable estimates of bioburden. This study brings together experiments performed by NASA and the European Space Agency with approved swab and wipe sampling devices, inoculating steel coupons with laboratory strains of Bacillus spp. spores commonly recovered from spacecraft assembly clean rooms (B. atrophaeus, B. megaterium, B. safensis and B. thuringiensis), with a mathematical model of the assay process to assess recovery efficiency. The statistical treatment developed in this study allows comparison of bioburden estimates made from different devices processed by different methods. This study also gives stakeholders and practitioners a statistically rigorous approach to predict bioburden that can be folded into future modeling efforts.
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Affiliation(s)
- Michael DiNicola
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| | - Arman Seuylemezian
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| | - Lisa Guan
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| | - Christine Moissl-Eichinger
- Medical University of Graz, Diagnostic and Research Institute of Hygiene, Microbiology, and Environmental Medicine, Graz, Austria
| | - Amy Baker
- SETI Institute, Mountain View, California, USA
| | - Jason Johns
- Herndon Solutions Group, Kennedy Space Center, Merritt Island, Florida, USA
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Kimura S, Ishikawa S, Hayashi N, Fujita K, Inatomi Y, Suzuki S. Bacterial and fungal bioburden reduction on material surfaces using various sterilization techniques suitable for spacecraft decontamination. Front Microbiol 2023; 14:1253436. [PMID: 38152378 PMCID: PMC10751312 DOI: 10.3389/fmicb.2023.1253436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Accepted: 11/28/2023] [Indexed: 12/29/2023] Open
Abstract
Planetary protection is a guiding principle aiming to prevent microbial contamination of the solar system by spacecraft (forward contamination) and extraterrestrial contamination of the Earth (backward contamination). Bioburden reduction on spacecraft, including cruise and landing systems, is required to prevent microbial contamination from Earth during space exploration missions. Several sterilization methods are available; however, selecting appropriate methods is essential to eliminate a broad spectrum of microorganisms without damaging spacecraft components during manufacturing and assembly. Here, we compared the effects of different bioburden reduction techniques, including dry heat, UV light, isopropyl alcohol (IPA), hydrogen peroxide (H2O2), vaporized hydrogen peroxide (VHP), and oxygen and argon plasma on microorganisms with different resistance capacities. These microorganisms included Bacillus atrophaeus spores and Aspergillus niger spores, Deinococcus radiodurans, and Brevundimonas diminuta, all important microorganisms for considering planetary protection. Bacillus atrophaeus spores showed the highest resistance to dry heat but could be reliably sterilized (i.e., under detection limit) through extended time or increased temperature. Aspergillus niger spores and D. radiodurans were highly resistant to UV light. Seventy percent of IPA and 7.5% of H2O2 treatments effectively sterilized D. radiodurans and B. diminuta but showed no immediate bactericidal effect against B. atrophaeus spores. IPA immediately sterilized A. niger spores, but H2O2 did not. During VHP treatment under reduced pressure, viable B. atrophaeus spores and A. niger spores were quickly reduced by approximately two log orders. Oxygen plasma sterilized D. radiodurans but did not eliminate B. atrophaeus spores. In contrast, argon plasma sterilized B. atrophaeus but not D. radiodurans. Therefore, dry heat could be used for heat-resistant component bioburden reduction, and VHP or plasma for non-heat-resistant components in bulk bioburden reduction. Furthermore, IPA, H2O2, or UV could be used for additional surface bioburden reduction during assembly and testing. The systemic comparison of sterilization efficiencies under identical experimental conditions in this study provides basic criteria for determining which sterilization techniques should be selected during bioburden reduction for forward planetary protection.
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Affiliation(s)
- Shunta Kimura
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Japan
- Space Exploration Innovation Hub Center, Japan Aerospace Exploration Agency, Sagamihara, Japan
- Graduate Institute for Advanced Studies, SOKENDAI, Sagamihara, Japan
| | - Shu Ishikawa
- Engineering Division, Kajima Corporation, Tokyo, Japan
| | - Nobuya Hayashi
- Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Fukuoka, Japan
| | - Kazuhisa Fujita
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Japan
- Safety and Mission Assurance Department, Japan Aerospace Exploration Agency, Tsukuba, Japan
| | - Yuko Inatomi
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Japan
- Space Exploration Innovation Hub Center, Japan Aerospace Exploration Agency, Sagamihara, Japan
- Graduate Institute for Advanced Studies, SOKENDAI, Sagamihara, Japan
| | - Shino Suzuki
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Japan
- Space Exploration Innovation Hub Center, Japan Aerospace Exploration Agency, Sagamihara, Japan
- Graduate Institute for Advanced Studies, SOKENDAI, Sagamihara, Japan
- Geobiology and Astrobiology Laboratory, RIKEN Cluster for Pioneering Research, Wako, Saitama, Japan
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