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Richter WR, Sunderman MM, Schaeufele DJ, Willenberg Z, Ratliff K, Calfee MW, Oudejans L. Evaluation of steam heat as a decontamination approach for SARS-CoV-2 when applied to common transit-related materials. J Appl Microbiol 2023; 134:lxad053. [PMID: 36906281 PMCID: PMC10257936 DOI: 10.1093/jambio/lxad053] [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: 11/30/2023] [Revised: 01/31/2023] [Accepted: 03/10/2023] [Indexed: 03/13/2023]
Abstract
AIMS The purpose of this study was to evaluate the efficacy of steam heat for inactivation of SARS-CoV-2 when applied to materials common in mass transit installations. METHODS AND RESULTS SARS CoV-2 (USA-WA1/2020) was resuspended in either cell culture media or synthetic saliva, inoculated (∼1 × 106 TCID50) onto porous and nonporous materials and subjected to steam inactivation efficacy tests as either wet or dried droplets. The inoculated test materials were exposed to steam heat ranging from 70°C to 90°C. The amount of infectious SARS-CoV-2 remaining after various exposure durations ranging from 1 to 60 s was assessed. Higher steam heat application resulted in higher inactivation rates at short contact times. Steam applied at 1-inch distance (∼90°C at the surface) resulted in complete inactivation for dry inoculum within 2 s of exposure (excluding two outliers of 19 test samples at the 5-s duration) and within 2-30 s of exposure for wet droplets. Increasing the distance to 2 inches (∼70°C) also increased the exposure time required to achieve complete inactivation to 15 or 30 s for materials inoculated with saliva or cell culture media, respectively. CONCLUSIONS Steam heat can provide high levels of decontamination (>3 log reduction) for transit-related materials contaminated with SARS-CoV-2 using a commercially available steam generator with a manageable exposure time of 2-5 s.
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Affiliation(s)
| | | | | | | | - Katherine Ratliff
- U.S. Environmental Protection Agency, Office of Research and Development, Center for Environmental Solutions and Emergency Response, Research Triangle Park, NC 27711, United States
| | - M. Worth Calfee
- U.S. Environmental Protection Agency, Office of Research and Development, Center for Environmental Solutions and Emergency Response, Research Triangle Park, NC 27711, United States
| | - Lukas Oudejans
- U.S. Environmental Protection Agency, Office of Research and Development, Center for Environmental Solutions and Emergency Response, Research Triangle Park, NC 27711, United States
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Richter WR, Sunderman MM, Fulton ML, Willenberg Z, Serre S, Oudejans L, Wood J, Calfee MW. Decontamination efficacy of common liquid disinfectants against non-spore-forming biological agents in soil matrices. J Appl Microbiol 2022; 133:3659-3668. [PMID: 36056613 PMCID: PMC9748868 DOI: 10.1111/jam.15802] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Revised: 07/20/2022] [Accepted: 08/28/2022] [Indexed: 11/28/2022]
Abstract
AIMS The purpose of this study was to evaluate decontamination efficacy, within three soil types, against Yersinia pestis, Burkholderia pseudomallei, and the Venezuelan Equine Encephalitis virus (VEEV). METHODS AND RESULTS One of three liquid disinfectants (dilute bleach, Virkon-S or Klozur One) was added to three soil types (sand, loam, or clay) and allowed contact for four pre-spike durations: 0, 15, 30 and 60 min. Y. pestis, B. pseudomallei, or VEEV was then spiked into the soil (10 microliters or approx. 1 × 107 CFU or PFU into 1 g soil) and decontamination efficacy assessed at post-spike contact times of 10 or 60 min at ambient environmental conditions. Across all soil types, sandy soil resulted in the least quenching to all three disinfectants tested as shown by sustained decontamination efficacy across all pre-spike and post-spike timepoints. Clay and loam soil types exhibited quenching effects on the hypochlorite and peroxygen based disinfectants (dilute bleach and Virkon S) and in general resulted in decreased efficacy with increased pre-spike contact time. The sodium persulfate (Klozur One) performance was the most consistent across all soil types and pre-spike contact times, resulting in greater efficacy with increased post-spike time. CONCLUSIONS Liquid disinfectants can provide high levels of decontamination in soil for both viral and non-spore-forming bacterial select agents. Hypochlorite and peroxygen based disinfectants used in soils containing higher organic content (loam or clay) may require extended contact times or re-application of liquid disinfectant, in as little as 15 min of application, to achieve a 6-log reduction. SIGNIFICANCE AND IMPACT OF THE STUDY These results provide information for the performance of three disinfectants in soil against non-spore-forming select agents. These data may aid response decision makers following a biological contamination incident by informing the selection of disinfectant as well as the re-application time to achieve effective site remediation.
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Affiliation(s)
| | | | | | | | - Shannon Serre
- US Environmental Protection Agency, TW Alexander Drive, Research Triangle Park, North Carolina, USA
| | - Lukas Oudejans
- US Environmental Protection Agency, TW Alexander Drive, Research Triangle Park, North Carolina, USA
| | - Joseph Wood
- US Environmental Protection Agency, TW Alexander Drive, Research Triangle Park, North Carolina, USA
| | - Michael W. Calfee
- US Environmental Protection Agency, TW Alexander Drive, Research Triangle Park, North Carolina, USA
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Richter W, Sunderman M, Willenberg Z, Calfee M, Serre S, Wood JP. Effectiveness of formaldehyde in various soil types as a wide area decontamination approach for Bacillus anthracis spores. PLoS One 2022; 17:e0277941. [PMID: 36399484 PMCID: PMC9674150 DOI: 10.1371/journal.pone.0277941] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Accepted: 11/07/2022] [Indexed: 11/20/2022] Open
Abstract
The purpose of this study was to evaluate and compare the decontamination efficacy of liquid formaldehyde solutions for three soil types (sand, loam, and clay) against spores of Bacillus anthracis (B.a.) and Bacillus atrophaeus. Approximately 1 x 108 colony forming units were inoculated into each sample. Through a series of six bench-scale experiments, two concentrations and two volumes of liquid formaldehyde solution were then added to the soil samples and allowed to remain in contact for either 24 or 48 hours. Decontamination efficacy was assessed at either 22° or 10°C with or without lids atop the sample jars. Complete inactivation (no spores recovered from the soil samples, typically providing > 7 log reduction) of B.a. occurred in all soil types in five of the six tests, while complete inactivation of B. atrophaeus was achieved in all soil types for three of the six tests. The results demonstrated a higher probability of complete inactivation of spores for samples that were covered, samples that received the higher volume of formaldehyde, and those contaminated with B.a. Overall, the use of liquid formaldehyde solution (2.5-5%) was highly effective in inactivating entire spore populations (typically > 107 CFU) for both B.a. and B. atrophaeus in the soil matrices studied. Covering the soil after application would allow for less formaldehyde solution to be used without impacting the overall efficacy of the process. The data from this study may aid in the selection of appropriate decontamination parameters when using liquid formaldehyde for soil remediation. The data may also aid in the decision to use B. atrophaeus as a surrogate for B.a. when performing further decontamination studies using liquid formalin solutions.
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Affiliation(s)
- William Richter
- Battelle Memorial Institute, Columbus, OH, United States of America
| | | | | | - Michael Calfee
- US Environmental Protection Agency, Research Triangle Park, NC, United States of America
| | - Shannon Serre
- US Environmental Protection Agency, Research Triangle Park, NC, United States of America
| | - Joseph P. Wood
- US Environmental Protection Agency, Research Triangle Park, NC, United States of America,* E-mail:
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4
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Richter WR, Sunderman MM, Mera TO, O’Brien KA, Morgan K, Streams S. Evaluation of environmental conditions as a decontamination approach for
SARS‐CoV
‐2 when applied to common library, archive, and museum related materials. J Appl Microbiol 2022; 132:3405-3415. [PMID: 35094472 PMCID: PMC9306959 DOI: 10.1111/jam.15468] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 01/24/2022] [Accepted: 01/25/2022] [Indexed: 12/02/2022]
Abstract
Aims The purpose of this study was to evaluate the effects of ambient or altered environmental conditions on the inactivation of SARS‐CoV‐2 applied to materials common in libraries, archives and museums. Methods and Results Porous and non‐porous materials (e.g. paper, plastic protective book cover) were inoculated with approximately 1 × 105 TCID50 SARS CoV‐2 (USA‐WA1/2020), dried, placed within test chamber in either a stacked or unstacked configuration, and exposed to environmental conditions ranging from 4 to 29°C at 40 ± 10% relative humidity. The amount of infectious SARS‐CoV‐2 was then assessed at various timepoints from 0 to 10 days. Ambient conditions resulted in varying inactivation rates per material type. Virus inactivation rate decreased when materials were stacked or at colder temperatures. Virus inactivation rate increased when materials were unstacked or at warmer temperatures. Conclusions SARS‐CoV‐2 at ambient conditions resulted in the inactivation of virus below limit of quantitation (LOQ) for all materials by Day 8. Warmer temperatures, for a subset of materials, increased SARS‐CoV‐2 inactivation, and all were <LOQ by Day 3. Significance and Impact of the Study These results provide information for the library, archives and museum community regarding the inactivation of SARS‐CoV‐2, showing that inactivation is possible using prescribed environmental conditions and is a potential method of decontamination for items not compatible with common liquid disinfectants.
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Affiliation(s)
| | | | - T. O. Mera
- Battelle Memorial Institute Columbus OH USA
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5
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Choi YW, Sunderman MM, McCauley MW, Richter WR, Willenberg ZJ, Wood J, Serre S, Mickelsen L, Willison S, Rupert R, Muñiz-Ortiz JG, Casey S, Calfee MW. Decontamination of Bacillus Spores with Formaldehyde Vapor under Varied Environmental Conditions. APPLIED BIOSAFETY 2021; 26:139-53. [PMID: 32982605 PMCID: PMC7511015 DOI: 10.1089/apb.21.926975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Introduction This study investigated formaldehyde decontamination efficacy against dried Bacillus spores on porous and non-porous test surfaces, under various environmental conditions. This knowledge will help responders determine effective formaldehyde exposure parameters to decontaminate affected spaces following a biological agent release. Methods Prescribed masses of paraformaldehyde or formalin were sublimated or evaporated, respectively, to generate formaldehyde vapor within a bench-scale test chamber. Adsorbent cartridges were used to measure formaldehyde vapor concentrations in the chamber at pre-determined times. A validated method was used to extract the cartridges and analyze for formaldehyde via liquid chromatography. Spores of Bacillus globigii, Bacillus thuringiensis, and Bacillus anthracis were inoculated and dried onto porous bare pine wood and non-porous painted concrete material coupons. A series of tests was conducted where temperature, relative humidity, and formaldehyde concentration were varied, to determine treatment efficacy outside of conditions where this decontaminant is well-characterized (laboratory temperature and humidity and 12 mg/L theoretical formaldehyde vapor concentration) to predict decontamination efficacy in applications that may arise following a biological incident. Results Low temperature trials (approximately 10°C) resulted in decreased formaldehyde air concentrations throughout the 48-hour time-course when compared with formaldehyde concentrations collected in the ambient temperature trials (approximately 22°C). Generally, decontamination efficacy on wood was lower for all three spore types compared with painted concrete. Also, higher recoveries resulted from painted concrete compared to wood, consistent with historical data on these materials. The highest decontamination efficacies were observed on the spores subjected to the longest exposures (48 hours) on both materials, with efficacies that gradually decreased with shorter exposures. Adsorption or absorption of the formaldehyde vapor may have been a factor, especially during the low temperature trials, resulting in less available formaldehyde in the air when measured. Conclusion Environmental conditions affect formaldehyde concentrations in the air and thereby affect decontamination efficacy. Efficacy is also impacted by the material with which the contaminants are in contact.
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Affiliation(s)
| | | | | | | | | | - Joseph Wood
- US Environmental Protection Agency, TW Alexander Drive, Research Triangle Park, NC, USA
| | - Shannon Serre
- US Environmental Protection Agency, TW Alexander Drive, Research Triangle Park, NC, USA
| | - Leroy Mickelsen
- US Environmental Protection Agency, TW Alexander Drive, Research Triangle Park, NC, USA
| | | | - Rich Rupert
- US Environmental Protection Agency, Region 3, Philadelphia, PA
| | | | - Sara Casey
- United Kingdom, Department for Environment, Food and Rural Affairs, CBRN Recovery Team, Stafford, England
| | - M Worth Calfee
- US Environmental Protection Agency, TW Alexander Drive, Research Triangle Park, NC, USA
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Choi YW, Sunderman MM, McCauley MW, Richter WR, Willenberg ZJ, Wood J, Serre S, Mickelsen L, Willison S, Rupert R, Muñiz Ortiz JG, Casey S, Calfee MW. Formaldehyde Vapor Characteristics in Varied Decontamination Environments. APPLIED BIOSAFETY 2021; 26:33-41. [PMID: 34017220 DOI: 10.1089/apb.21.926968] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Introduction This effort investigated formaldehyde vapor characteristics under various environmental conditions by the analyses of air samples collected over a time-course. This knowledge will help responders achieve desired formaldehyde exposure parameters for decontamination of affected spaces after a biological contamination incident. Methods Prescribed masses of paraformaldehyde and formalin were sublimated or evaporated, respectively, to generate formaldehyde vapor. Adsorbent cartridges were used to collect air samples from the test chamber at predetermined times. A validated method was used to extract the cartridges and analyze for formaldehyde via liquid chromatography. In addition, material demand for the formaldehyde was evaluated by inclusion of arrays of Plexiglas panels in the test chamber to determine the impact of varied surface areas within the test chamber. Temperature was controlled with a circulating water bath connected to a radiator and fan inside the chamber. Relative humidity was controlled with humidity fixed-point salt solutions and water vapor generated from evaporated water. Results Low temperature trials (approximately 10°C) resulted in decreased formaldehyde air concentrations throughout the 48-hour time-course when compared with formaldehyde concentrations in the ambient temperature trials (approximately 22°C). The addition of clear Plexiglas panels to increase the surface area of the test chamber interior resulted in appreciable decreases of formaldehyde air concentration when compared to an empty test chamber. Conclusion This work has shown that environmental variables and surface-to-volume ratios in the decontaminated space may affect the availability of formaldehyde in the air and, therefore, may affect decontamination effectiveness.
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Affiliation(s)
| | | | | | | | | | - Joseph Wood
- US Environmental Protection Agency, Research Triangle Park, NC, USA
| | - Shannon Serre
- US Environmental Protection Agency, Research Triangle Park, NC, USA
| | - Leroy Mickelsen
- US Environmental Protection Agency, Research Triangle Park, NC, USA
| | | | - Rich Rupert
- US Environmental Protection Agency, Region 3, Philadelphia, PA, USA
| | | | - Sara Casey
- Department for Environment, Food and Rural Affairs, CBRN Recovery Team, Stafford, UK
| | - M Worth Calfee
- US Environmental Protection Agency, Research Triangle Park, NC, USA
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Airborne Disinfection by Dry Fogging Efficiently Inactivates Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), Mycobacteria, and Bacterial Spores and Shows Limitations of Commercial Spore Carriers. Appl Environ Microbiol 2021; 87:AEM.02019-20. [PMID: 33158901 PMCID: PMC7848922 DOI: 10.1128/aem.02019-20] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Accepted: 11/05/2020] [Indexed: 11/30/2022] Open
Abstract
Airborne disinfection is not only of crucial importance for the safe operation of laboratories and animal rooms where infectious agents are handled but also can be used in public health emergencies such as the current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. We show that dry fogging an aerosolized mixture of peroxyacetic acid and hydrogen peroxide (aPAA-HP) is highly microbicidal, efficient, fast, robust, environmentally neutral, and a suitable airborne disinfection method. Airborne disinfection of high-containment facilities before maintenance or between animal studies is crucial. Commercial spore carriers (CSC) coated with 106 spores of Geobacillus stearothermophilus are often used to assess the efficacy of disinfection. We used quantitative carrier testing (QCT) procedures to compare the sensitivity of CSC with that of surrogates for nonenveloped and enveloped viruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), mycobacteria, and spores, to an aerosolized mixture of peroxyacetic acid and hydrogen peroxide (aPAA-HP). We then used the QCT methodology to determine relevant process parameters to develop and validate effective disinfection protocols (≥4-log10 reduction) in various large and complex facilities. Our results demonstrate that aPAA-HP is a highly efficient procedure for airborne room disinfection. Relevant process parameters such as temperature and relative humidity can be wirelessly monitored. Furthermore, we found striking differences in inactivation efficacies against some of the tested microorganisms. Overall, we conclude that dry fogging a mixture of aPAA-HP is highly effective against a broad range of microorganisms as well as material compatible with relevant concentrations. Furthermore, CSC are artificial bioindicators with lower resistance and thus should not be used for validating airborne disinfection when microorganisms other than viruses have to be inactivated. IMPORTANCE Airborne disinfection is not only of crucial importance for the safe operation of laboratories and animal rooms where infectious agents are handled but also can be used in public health emergencies such as the current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. We show that dry fogging an aerosolized mixture of peroxyacetic acid and hydrogen peroxide (aPAA-HP) is highly microbicidal, efficient, fast, robust, environmentally neutral, and a suitable airborne disinfection method. In addition, the low concentration of dispersed disinfectant, particularly for enveloped viral pathogens such as SARS-CoV-2, entails high material compatibility. For these reasons and due to the relative simplicity of the procedure, it is an ideal disinfection method for hospital wards, ambulances, public conveyances, and indoor community areas. Thus, we conclude that this method is an excellent choice for control of the current SARS-CoV-2 pandemic.
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Häcker I, Koller R, Eichner G, Martin J, Liapi E, Rühl J, Rehling T, Schetelig MF. Evaluation of Hydrogen Peroxide Fumigation and Heat Treatment for Standard Emergency Arthropod Inactivation in BSL-3 Insectaries. Front Bioeng Biotechnol 2020; 8:602937. [PMID: 33304894 PMCID: PMC7701145 DOI: 10.3389/fbioe.2020.602937] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Accepted: 10/20/2020] [Indexed: 11/13/2022] Open
Abstract
Climate change and global movements of people and goods have accelerated the spread of invasive species, including insects that vector infectious diseases, which threaten the health of more than half of the world’s population. Increasing research efforts to control these diseases include the study of vector – pathogen interactions, involving the handling of pathogen-infected vector insects under biosafety level (BSL) 2 and 3 conditions. Like microbiology BSL-3 laboratories, BSL-3 insectaries are usually subjected to fixed-term or emergency room decontamination using recognized methods such as hydrogen peroxide (H2O2) or formaldehyde fumigation. While these procedures have been standardized and approved for the inactivation of diverse pathogens on surfaces, to date, there are no current standards for effective room-wide inactivation of insects in BSL-3 facilities in case of an emergency such as the accidental release of a large number of infected vectors. As H2O2 is often used for standard room decontamination in BSL-3 facilities, we evaluated H2O2 fumigation as a potential standard method for the safe, room-wide deactivation of insects in BSL-3 insectaries in comparison to heat treatment. To account for physiological diversity in vector insect species, six species from three different orders were tested. For the H2O2 fumigation we observed a strong but also varying resilience across all species. Lethal exposure time for the tested dipterans ranged from nine to more than 24 h. Furthermore, the coleopteran, Tribolium castaneum, did not respond to continuous H2O2 exposure for 48 h under standard room decontamination conditions. In contrast, temperatures of 50°C effectively killed all the tested species within 2 to 10 min. The response to lower temperatures (40–48°C) again showed a strong variation between species. In summary, results suggest that H2O2 fumigation, especially in cases where a gas generator is part of the laboratory equipment, may be used for the inactivation of selected species but is not suitable as a general emergency insect inactivation method under normal room decontamination conditions. In contrast, heat treatment at 48 to 50°C has the potential to be developed as an approved standard procedure for the effective inactivation of insects in BSL-3 facilities.
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Affiliation(s)
- Irina Häcker
- Department of Insect Biotechnology in Plant Protection, Institute for Insect Biotechnology, Justus-Liebig-University Gießen, Gießen, Germany.,Department of Insect Pest and Vector Control, Division of Bioresources, Fraunhofer Institute for Molecular Biology and Applied Ecology (IME), Gießen, Germany
| | - Roland Koller
- Ortner Reinraumtechnik GmbH (Ortner Cleanrooms Unlimited), Villach, Austria
| | - Gerrit Eichner
- Mathematical Institute, Justus-Liebig-University Gießen, Gießen, Germany
| | - Jakob Martin
- Department of Insect Biotechnology in Plant Protection, Institute for Insect Biotechnology, Justus-Liebig-University Gießen, Gießen, Germany
| | - Eleni Liapi
- Department of Biochemistry and Biotechnology, University of Thessaly, Larissa, Greece
| | - Johanna Rühl
- Department of Insect Biotechnology in Plant Protection, Institute for Insect Biotechnology, Justus-Liebig-University Gießen, Gießen, Germany
| | - Tanja Rehling
- Department of Insect Biotechnology in Plant Protection, Institute for Insect Biotechnology, Justus-Liebig-University Gießen, Gießen, Germany
| | - Marc F Schetelig
- Department of Insect Biotechnology in Plant Protection, Institute for Insect Biotechnology, Justus-Liebig-University Gießen, Gießen, Germany.,Department of Insect Pest and Vector Control, Division of Bioresources, Fraunhofer Institute for Molecular Biology and Applied Ecology (IME), Gießen, Germany
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9
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Wang Z, Kowal SF, Carslaw N, Kahan TF. Photolysis-driven indoor air chemistry following cleaning of hospital wards. INDOOR AIR 2020; 30:1241-1255. [PMID: 32485006 DOI: 10.1111/ina.12702] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 04/17/2020] [Accepted: 05/19/2020] [Indexed: 05/25/2023]
Abstract
Effective cleaning techniques are essential for the sterilization of rooms in hospitals and industry. No-touch devices (NTDs) that use fumigants such as hydrogen peroxide (H2 O2 ), formaldehyde (HCHO), ozone (O3 ), and chlorine dioxide (OClO) are a recent innovation. This paper reports a previously unconsidered potential consequence of such cleaning technologies: the photochemical formation of high concentrations of hydroxyl radicals (OH), hydroperoxy radicals (HO2 ), organic peroxy radicals (RO2 ), and chlorine radicals (Cl) which can form harmful reaction products when exposed to chemicals commonly found in indoor air. This risk was evaluated by calculating radical production rates and concentrations based on measured indoor photon fluxes and typical fumigant concentrations during and after cleaning events. Sunlight and fluorescent tubes without covers initiated photolysis of all fumigants, and plastic-covered fluorescent tubes initiated photolysis of only some fumigants. Radical formation was often dominated by photolysis of fumigants during and after decontamination processes. Radical concentrations were predicted to be orders of magnitude greater than background levels during and immediately following cleaning events with each fumigant under one or more illumination condition. Maximum predicted radical concentrations (1.3 × 107 molecule cm-3 OH, 2.4 ppb HO2 , 6.8 ppb RO2 and 2.2 × 108 molecule cm-3 Cl) were much higher than baseline concentrations. Maximum OH concentrations occurred with O3 photolysis, HO2 with HCHO photolysis, and RO2 and Cl with OClO photolysis. Elevated concentrations may persist for hours after NTD use, depending on the air change rate and air composition. Products from reactions involving radicals could significantly decrease air quality when disinfectants are used, leading to adverse health effects for occupants.
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Affiliation(s)
- Zixu Wang
- Department of Environment and Geography, University of York, York, UK
| | - Shawn F Kowal
- Department of Chemistry, Syracuse University, Syracuse, NY, USA
| | - Nicola Carslaw
- Department of Environment and Geography, University of York, York, UK
| | - Tara F Kahan
- Department of Chemistry, Syracuse University, Syracuse, NY, USA
- Department of Chemistry, University of Saskatchewan, Saskatoon, SK, Canada
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10
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Grimaldo MA, Bouyer DH, de Siqueira CLM. Determining the Effectiveness of Decontamination with Ionized Hydrogen Peroxide. APPLIED BIOSAFETY 2020; 25:134-141. [PMID: 36035760 PMCID: PMC9134624 DOI: 10.1177/1535676020935405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/17/2023]
Abstract
Introduction Ionized Hydrogen Peroxide (iHP) is a new technology used for the decontamination of surfaces or laboratory areas. It utilizes a low concentration of hydrogen peroxide (H2O2) mixed with air and ionized through a cold plasma arc. This technology generates reactive oxygen species (ROS) as a means of decontamination. Objectives The purpose of this study is to evaluate the diffusion effect of iHP and its decontamination capabilities using biological and enzyme indicators. Methods A gas-tight fumigation room with a volume of 880 ft3 was used for the decontamination trials. During the decontamination process, empty animal cages were placed inside to create fumigant distribution restrictions. Spore and enzyme indicators were placed in eleven locations throughout the decontamination room. Generation of iHP was done with the use of TOMI's SteraMist Environmental System and the SteraMist Solution, with 7.8% H2O2 at a dose of 0.5 ml per ft3. Results For the decontamination of 1hr, 2hrs, 6hrs, and 12hrs, the biological indicators of B. atrophaeus in Stainless Steel (SS) Disk in Tyvek envelope have an inactivation rate of 94%, 97%, 100%, and 100%, respectively. For G. stearothermophilus in SS disk and Tyvek envelope, it has 82%, 68%, 100%, and 100%, respectively and, for G. stearothermophilus in SS strips it has an effective rate of 88%, 67%, 91%, and 100%, respectively. Conclusion iHP inactivates spores, and the residual tAK activity indicates a gas-like fumigant diffusion due to the uniformity of the inactivation without the use of oscillating fans as the contact time is extended.
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Affiliation(s)
- Miguel A. Grimaldo
- Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brasil
- University of Texas Medical Branch, Galveston, TX, USA
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11
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Choi YW, Sunderman MM, McCauley MW, Richter WR, Willenberg ZJ, Wood J, Serre S, Mickelsen L, Willison S, Rupert R, Ortiz JGM, Casey S, Calfee MW. Decontamination of Bacillus Spores with Formaldehyde Vapor Under Varied Environmental Conditions. APPLIED BIOSAFETY 2020. [DOI: 10.1177/1535676020926975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Introduction: This effort investigated formaldehyde vapor characteristics under various environmental conditions by the analyses of air samples collected over a time-course. This knowledge will help responders achieve desired formaldehyde exposure parameters for decontamination of affected spaces after a biological contamination incident. Methods: Prescribed masses of paraformaldehyde and formalin were sublimated or evaporated, respectively, to generate formaldehyde vapor. Adsorbent cartridges were used to collect air samples from the test chamber at predetermined times. A validated method was used to extract the cartridges and analyze for formaldehyde via liquid chromatography. In addition, material demand for the formaldehyde was evaluated by inclusion of arrays of Plexiglas panels in the test chamber to determine the effect of varied surface areas within the test chamber. Temperature was controlled with a circulating water bath connected to a radiator and fan inside the chamber. Relative humidity was controlled with humidity fixed-point salt solutions and water vapor generated from evaporated water. Results: Low temperature trials (approximately 10°C) resulted in decreased formaldehyde air concentrations throughout the 48-hour time-course when compared with formaldehyde concentrations in the ambient temperature trials (approximately 22°C). The addition of clear Plexiglas panels to increase the surface area of the test chamber interior resulted in appreciable decreases of formaldehyde air concentration when compared to an empty test chamber. Conclusion: This work has shown that environmental variables and surface-to-volume ratios in the decontaminated space may affect the availability of formaldehyde in the air and, therefore, may affect decontamination effectiveness.
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Affiliation(s)
| | | | | | | | | | - Joseph Wood
- US Environmental Protection Agency, Research Triangle Park, NC, USA
| | - Shannon Serre
- US Environmental Protection Agency, Research Triangle Park, NC, USA
| | - Leroy Mickelsen
- US Environmental Protection Agency, Research Triangle Park, NC, USA
| | | | - Rich Rupert
- US Environmental Protection Agency, Region 3, Philadelphia, PA, USA
| | | | - Sara Casey
- Department for Environment, Food and Rural Affairs, CBRN Recovery Team, Stafford, UK
| | - M. Worth Calfee
- US Environmental Protection Agency, Research Triangle Park, NC, USA
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Choi YW, Sunderman MM, McCauley MW, Richter WR, Willenberg ZJ, Wood J, Serre S, Mickelsen L, Willison S, Rupert R, Ortiz JGM, Casey S, Calfee MW. Formaldehyde Vapor Characteristics in Varied Decontamination Environments. APPLIED BIOSAFETY 2020. [DOI: 10.1177/1535676020926968] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Introduction: This effort investigated formaldehyde vapor characteristics under various environmental conditions by the analyses of air samples collected over a time-course. This knowledge will help responders achieve desired formaldehyde exposure parameters for decontamination of affected spaces after a biological contamination incident. Methods: Prescribed masses of paraformaldehyde and formalin were sublimated or evaporated, respectively, to generate formaldehyde vapor. Adsorbent cartridges were used to collect air samples from the test chamber at predetermined times. A validated method was used to extract the cartridges and analyze for formaldehyde via liquid chromatography. In addition, material demand for the formaldehyde was evaluated by inclusion of arrays of Plexiglas panels in the test chamber to determine the impact of varied surface areas within the test chamber. Temperature was controlled with a circulating water bath connected to a radiator and fan inside the chamber. Relative humidity was controlled with humidity fixed-point salt solutions and water vapor generated from evaporated water. Results: Low temperature trials (approximately 10°C) resulted in decreased formaldehyde air concentrations throughout the 48-hour time-course when compared with formaldehyde concentrations in the ambient temperature trials (approximately 22°C). The addition of clear Plexiglas panels to increase the surface area of the test chamber interior resulted in appreciable decreases of formaldehyde air concentration when compared to an empty test chamber. Conclusion: This work has shown that environmental variables and surface-to-volume ratios in the decontaminated space may affect the availability of formaldehyde in the air and, therefore, may affect decontamination effectiveness.
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Affiliation(s)
| | | | | | | | | | - Joseph Wood
- US Environmental Protection Agency, Research Triangle Park, NC, USA
| | - Shannon Serre
- US Environmental Protection Agency, Research Triangle Park, NC, USA
| | - Leroy Mickelsen
- US Environmental Protection Agency, Research Triangle Park, NC, USA
| | | | - Rich Rupert
- US Environmental Protection Agency, Region 3, Philadelphia, PA, USA
| | | | - Sara Casey
- Department for Environment, Food and Rural Affairs, CBRN Recovery Team, Stafford, UK
| | - M. Worth Calfee
- US Environmental Protection Agency, Research Triangle Park, NC, USA
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13
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Stuart J, Chewins J, Tearle J. Comparing the Efficacy of Formaldehyde with Hydrogen Peroxide Fumigation on Infectious Bronchitis Virus. APPLIED BIOSAFETY 2020; 25:83-89. [PMID: 34191920 PMCID: PMC7307011 DOI: 10.1177/1535676020909998] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND The recent reclassification of formaldehyde as a presumed carcinogen prompted the investigation into the comparative efficacy of hydrogen peroxide as a fumigant in microbiological safety cabinets. INTRODUCTION The aim of the study was to quantify the biocidal efficacy of formaldehyde fumigation, including variables such as exposure time and concentration, and then to compare this to the biocidal efficacy achieved from a hydrogen peroxide vapor fumigation system. The study also investigated the ability of both fumigants to permeate the microbiological safety cabinet (MBSC), including the workspace, under the work tray, and after the HEPA filters. Furthermore, the effect of organic soiling on efficacy was also assessed. Infectious bronchitis virus (IBV) was used as the biological target to develop this study model. METHODS A model using IBV was developed to determine the efficacy of formaldehyde and hydrogen peroxide as fumigants. Virus was dried on stainless steel discs, and variables including concentration, time, protein soiling, and location within an MBSC were assessed. RESULTS It was demonstrated that formaldehyde fumigation could achieve a 6-log reduction in the titer of the virus throughout the cabinet, and high protein soiling in the presentation did not affect efficacy. Appropriate cycle parameters for the hydrogen peroxide system were developed, and when challenged with IBV, it was shown that vaporized hydrogen peroxide could achieve an equal 6-log titer reduction as formaldehyde within the cabinet workspace and overcome the presence of soiling. CONCLUSION Hydrogen peroxide was demonstrated to be a viable alternative to formaldehyde under most situations tested. However, the hydrogen peroxide system did not achieve an equal titer reduction above the cabinet's first HEPA filter using the cabinet workspace cycle, and further optimization of the hydrogen peroxide cycle parameters, including pulsing of the cabinet fans, may be required to achieve this.
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Wood JP, Wendling M, Richter W, Rogers J. The use of ozone gas for the inactivation of Bacillus anthracis and Bacillus subtilis spores on building materials. PLoS One 2020; 15:e0233291. [PMID: 32437373 PMCID: PMC7241793 DOI: 10.1371/journal.pone.0233291] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Accepted: 05/02/2020] [Indexed: 11/19/2022] Open
Abstract
A study was conducted to assess the efficacy of ozone gas in inactivating spores of both Bacillus anthracis and Bacillus subtilis inoculated onto six building materials (glass, wood, carpet, laminate, galvanized metal, and wallboard paper). Testing conditions consisted of ozone gas concentrations ranging from 7,000-12,000 parts per million (ppm), contact times from 4 to 12 h, and two relative humidity (RH) levels of 75 and 85%. Results showed that increasing the ozone concentration, contact time, and RH generally increased decontamination efficacy. The materials in which the highest decontamination efficacy was achieved for B. anthracis spores were wallboard paper, carpet, and wood with ≥ 6 log10 reduction (LR) occurring with 9,800 ppm ozone, 85% RH, for 6 h. The laminate and galvanized metal materials were generally more difficult to decontaminate, requiring 12,000 ppm ozone, 85% RH, and 9-12 h contact time to achieve ≥6 LR of B. anthracis. Lastly, overall, there were no significant differences in decontamination efficacy between the two species.
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Affiliation(s)
- Joseph P. Wood
- Office of Research and Development, U.S. Environmental Protection Agency, National Homeland Security Research Program, Research Triangle Park, North Carolina, United States of America
| | - Morgan Wendling
- Battelle Memorial Institute, Columbus, Ohio, United States of America
| | - William Richter
- Battelle Memorial Institute, Columbus, Ohio, United States of America
| | - James Rogers
- Battelle Memorial Institute, Columbus, Ohio, United States of America
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15
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Richter WR, Sunderman MM, Wendling MQS, Serre S, Mickelsen L, Rupert R, Wood J, Choi Y, Willenberg Z, Calfee MW. Evaluation of altered environmental conditions as a decontamination approach for nonspore-forming biological agents. J Appl Microbiol 2020; 128:1050-1059. [PMID: 31782200 PMCID: PMC7323857 DOI: 10.1111/jam.14532] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Revised: 10/11/2019] [Accepted: 11/21/2019] [Indexed: 01/04/2023]
Abstract
AIMS The purpose of this study was to evaluate the effects of altered environmental conditions on the persistence of Francisella tularensis bacteria and Venezuelan equine encephalitis virus (VEEV), on two material types. METHODS AND RESULTS Francisella tularensis (F.t.) and VEEV were inoculated (c. 1 × 108 colony-forming units or PFU), dried onto porous and nonporous fomites (glass and paper), and exposed to combinations of altered environmental conditions ranging from 22 to 60°C and 30 to 75% relative humidity (RH). Viability of test organism was assessed after contact times ranging from 30 min to 10 days. Inactivation rates of F.t. and VEEV increased as both temperature and/or RH were increased. Greater efficacy was observed for paper as compared to glass for both test organisms. CONCLUSIONS The use of elevated temperature and RH increased rate of inactivation for both organisms and greater than six log reduction was accomplished in as little as 6 h by elevating temperature to approximately 60°C. SIGNIFICANCE AND IMPACT OF THE STUDY These results provide information for inactivation of nonspore-forming select agents using elevated temperature and humidity which may aid incident commanders following a biological contamination incident by providing alternative methods for remediation.
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Affiliation(s)
- W R Richter
- Battelle Memorial Institute, Columbus, OH, USA
| | | | | | - S Serre
- US Environmental Protection Agency, Research Triangle Park, NC, USA
| | - L Mickelsen
- US Environmental Protection Agency, Research Triangle Park, NC, USA
| | - R Rupert
- US Environmental Protection Agency, Philadelphia, PA, USA
| | - J Wood
- US Environmental Protection Agency, Research Triangle Park, NC, USA
| | - Y Choi
- Battelle Memorial Institute, Columbus, OH, USA
| | | | - M W Calfee
- US Environmental Protection Agency, Research Triangle Park, NC, USA
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16
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Young CJ, Zhou S, Siegel JA, Kahan TF. Illuminating the dark side of indoor oxidants. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2019; 21:1229-1239. [PMID: 31173015 DOI: 10.1039/c9em00111e] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The chemistry of oxidants and their precursors (oxidants*) plays a central role in outdoor environments but its importance in indoor air remains poorly understood. Ozone (O3) chemistry is important in some indoor environments and, until recently, ozone was thought to be the dominant oxidant indoors. There is now evidence that formation of the hydroxyl radical by photolysis of nitrous acid (HONO) and formaldehyde (HCHO) may be important indoors. In the past few years, high time-resolution measurements of oxidants* indoors have become more common and the importance of event-based release of oxidants* during activities such as cleaning has been proposed. Here we review the current understanding of oxidants* indoors, including drivers of the formation and loss of oxidants*, levels of oxidants* in indoor environments, and important directions for future research.
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Affiliation(s)
- Cora J Young
- Department of Chemistry, York University, Canada.
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17
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Ishikawa S, Ueno S, Mitsui M, Matsumura Y, Hatsuoka T. Construction of Its Evaluation System in Originally Designed Test-Chamber System and Sporicidal Activity of Aerosolized Hypochlorite Solution to Bacillus subtilis Spores. Biocontrol Sci 2019; 24:57-65. [PMID: 30880314 DOI: 10.4265/bio.24.57] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
Abstract
Effective spatial disinfection systems are required for human health care, public hygiene, and food and medicine manufacturing. Although some aerosolized disinfectants were already applied to its purpose, accurate evaluation systems were under constructed. In this study, the spatial sporicidal activity of aerosolized hypochlorite solution (AHS) to dormant cells, Bacillus subtilis spores, was evaluated by an originally designed chamber system. In the test-chamber, AHS was supplied and existed as micro-droplets, and environmental relative humidity (RH) could be controlled. Available chlorine (AC) exposure was also controlled with appropriate AC loading but was influenced by the acidity of AHS. Our results indicated that inactivation of spore was depend on AC exposure amount and time. On the other hand, unsaturated environmental RH markedly decreased spore inactivation. This study indicated that our test-chamber system can provide reproducible test data under a homogeneous air condition, and, thereby, that the data obtained by the chamber system should contribute to predicting the AC-required dose to disinfect a whole building.
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Affiliation(s)
| | | | - Mai Mitsui
- Engineering Division, Kajima Corporation
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18
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Wood JP, Adrion AC. Review of Decontamination Techniques for the Inactivation of Bacillus anthracis and Other Spore-Forming Bacteria Associated with Building or Outdoor Materials. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:4045-4062. [PMID: 30901213 PMCID: PMC6547374 DOI: 10.1021/acs.est.8b05274] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Since the intentional release of Bacillus anthracis spores through the U.S. Postal Service in the fall of 2001, research and development related to decontamination for this biological agent have increased substantially. This review synthesizes the advances made relative to B. anthracis spore decontamination science and technology since approximately 2002, referencing the open scientific literature and publicly available, well-documented scientific reports. In the process of conducting this review, scientific knowledge gaps have also been identified. This review focuses primarily on techniques that are commercially available and that could potentially be used in the large-scale decontamination of buildings and other structures, as well as outdoor environments. Since 2002, the body of scientific data related to decontamination and microbial sterilization has grown substantially, especially in terms of quantifying decontamination efficacy as a function of several factors. Specifically, progress has been made in understanding how decontaminant chemistry, the materials the microorganisms are associated with, environmental factors, and microbiological methods quantitatively impact spore inactivation. While advancement has been made in the past 15 years to further the state of the science in the inactivation of bacterial spores in a decontamination scenario, further research is warranted to close the scientific gaps that remain.
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Affiliation(s)
- Joseph P. Wood
- United States Environmental Protection Agency, Offce of Research and Development, National Homeland Security Research Center, Research Triangle Park, North Carolina United States
- Corresponding Author: Phone: (919) 541-5029;
| | - Alden Charles Adrion
- United States Environmental Protection Agency, Offce of Research and Development, National Homeland Security Research Center, Research Triangle Park, North Carolina United States
- Oak Ridge Institute for Science and Education Postdoctoral Fellow, Oak Ridge, Tennessee 37830, United States
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19
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Richter WR, Wood JP, Wendling MQS, Rogers JV. Inactivation of Bacillus anthracis spores to decontaminate subway railcar and related materials via the fogging of peracetic acid and hydrogen peroxide sporicidal liquids. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2018; 206:800-806. [PMID: 29174643 PMCID: PMC5738270 DOI: 10.1016/j.jenvman.2017.11.027] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Revised: 11/08/2017] [Accepted: 11/09/2017] [Indexed: 05/23/2023]
Abstract
The inactivation of Bacillus anthracis spores on subway and used subway railcar materials was evaluated using fogged peracetic acid/hydrogen peroxide (PAA) and hydrogen peroxide (H2O2). A total of 21 separate decontamination tests were conducted using bacterial spores of both B. anthracis Ames (B.a.) and Bacillus atrophaeus (B.g.) inoculated onto several types of materials. Tests were conducted using commercial off-the-shelf fogging equipment filled with either PAA or H2O2 to fumigate a ∼15 cubic meter chamber under uncontrolled ambient relative humidity and controlled temperature (10 or 20 °C) from 8 to 168 h. For the present study, no conditions were found that resulted in complete inactivation of either B.a. Ames or B.g. on all test materials. Approximately 41% and 38% of the decontamination efficacies for B.a. and B.g., respectively, exhibited ≥6 log10 reduction (LR); efficacy depended greatly on the material. When testing at 10 °C, the mean LR was consistently lower for both B.a. and B.g. as compared to 20 °C. Based on the statistical comparison of the LR results, B.g. exhibited equivalent or greater resistance than B.a. for approximately 92% of the time across all 21 tests. The efficacy data suggest that B.g. may be a suitable surrogate for B.a. Ames when assessing the decontamination efficacy of fogged PAA or H2O2. Moreover, the results of this testing indicate that in the event of B.a. spore release into a subway system, the fogging of PAA or H2O2 represents a decontamination option for consideration.
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Affiliation(s)
| | - Joseph P Wood
- U.S. Environmental Protection Agency, National Homeland Security Research Center, Research Triangle Park, NC, USA
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20
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Robertson JM, Anders DL, Basalyga F, Millar J, Slack DP, Bever R. Effect of Sterilants on Amplification and Detection of Target DNA from Bacillus cereus Spores. J Forensic Sci 2017; 63:699-707. [PMID: 29139119 DOI: 10.1111/1556-4029.13653] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Revised: 08/28/2017] [Accepted: 08/29/2017] [Indexed: 11/28/2022]
Abstract
To conceal criminal activity of a bioterrorist or agroterrorist, the site of pathogen generation is often treated with sterilants to kill the organisms and remove evidence. As dead organisms cannot be analyzed by culture, this study examined whether DNA from sterilant-treated Bacillus cereus spores was viable for amplification. The spores were exposed to five common sterilants: bleach, Sterilox®, oxidizer foam (L-Gel), a peroxyacid (Actril®), and formaldehyde vapor. The spores were inoculated on typical surfaces found in offices and laboratories to test for environmental effects. It was found that the surface influenced the efficiency of recovery of the organisms. The DNA isolated from the recovered spores was successfully detected using RT-qPCR for all treatments except for formaldehyde, by amplifying the phosphatidylinositol phospholipase C and sphingomyelinase genes. The results demonstrated that evidence from sites treated with sterilants can still provide information on the uncultured organism, using DNA amplification.
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Affiliation(s)
- James M Robertson
- Counterterrorism and Forensic Science Research Unit, FBI Laboratory, Quantico, VA, 22135
| | - Douglas L Anders
- Scientific Response Analysis Unit, FBI Laboratory, Quantico, VA, 22135
| | | | - Julie Millar
- Bode Cellmark Forensics, Inc., Lorton, VA, 22079
| | | | - Robert Bever
- Bode Cellmark Forensics, Inc., Lorton, VA, 22079
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21
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Guan J, Chan M, Brooks BW, Rohonczy E, Miller LP. Vehicle and Equipment Decontamination During Outbreaks of Notifiable Animal Diseases in Cold Weather. APPLIED BIOSAFETY 2017. [DOI: 10.1177/1535676017719846] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Affiliation(s)
- Jiewen Guan
- Canadian Food Inspection Agency, Ottawa, Ontario, Canada
| | - Maria Chan
- Canadian Food Inspection Agency, Ottawa, Ontario, Canada
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22
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Affiliation(s)
- Didier Ngabo
- Public Health England, Porton, Salisbury, Wiltshire, UK
| | | | - Allan Bennett
- Public Health England, Porton, Salisbury, Wiltshire, UK
| | - Simon Parks
- Public Health England, Porton, Salisbury, Wiltshire, UK
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23
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Mott T, Shoe J, Hunter M, Woodson A, Fritts K, Klimko C, Quirk A, Welkos S, Cote C. Comparison of sampling methods to recover germinatedBacillus anthracisandBacillus thuringiensisendospores from surface coupons. J Appl Microbiol 2017; 122:1219-1232. [DOI: 10.1111/jam.13418] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Revised: 02/03/2017] [Accepted: 02/04/2017] [Indexed: 11/26/2022]
Affiliation(s)
- T.M. Mott
- Bacteriology Division; United States Army Medical Research Institute of Infectious Disease (USAMRIID); Frederick MD USA
| | - J.L. Shoe
- Bacteriology Division; United States Army Medical Research Institute of Infectious Disease (USAMRIID); Frederick MD USA
| | - M. Hunter
- Bacteriology Division; United States Army Medical Research Institute of Infectious Disease (USAMRIID); Frederick MD USA
| | - A.M. Woodson
- Bacteriology Division; United States Army Medical Research Institute of Infectious Disease (USAMRIID); Frederick MD USA
| | - K.A. Fritts
- Bacteriology Division; United States Army Medical Research Institute of Infectious Disease (USAMRIID); Frederick MD USA
| | - C.P. Klimko
- Bacteriology Division; United States Army Medical Research Institute of Infectious Disease (USAMRIID); Frederick MD USA
| | - A.V. Quirk
- Bacteriology Division; United States Army Medical Research Institute of Infectious Disease (USAMRIID); Frederick MD USA
| | - S.L. Welkos
- Bacteriology Division; United States Army Medical Research Institute of Infectious Disease (USAMRIID); Frederick MD USA
| | - C.K. Cote
- Bacteriology Division; United States Army Medical Research Institute of Infectious Disease (USAMRIID); Frederick MD USA
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24
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Wang T, Qi J, Wu J, Hao L, Yi Y, Lin S, Zhang Z. Response surface modeling for the inactivation of Bacillus subtilis subsp. niger spores by chlorine dioxide gas in an enclosed space. JOURNAL OF THE AIR & WASTE MANAGEMENT ASSOCIATION (1995) 2016; 66:508-517. [PMID: 26853499 DOI: 10.1080/10962247.2016.1150365] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
UNLABELLED Bacillus subtilis subsp. niger spores are a commonly used biological indicator to evaluate the disinfection of an enclosed space. In the present study, chlorine dioxide (ClO2) gas was applied to inactivate B. subtilis subsp. niger spores in an enclosed space. The effects of the ClO2 gas concentration (1-3 mg/l), relative humidity (RH, 30-70%) and exposure time (30-90 min) were investigated using a response surface methodology (RSM). A three-factor Box-Behnken experimental design was used. The obtained data were adequately fitted to a second-order polynomial model with an R2adj of 0.992. The ClO2 gas concentration, RH and exposure time all significantly (P<0.05) and positively correlated with the inactivation of B. subtilis subsp. niger spores. The interaction between the ClO2 gas concentration and RH as well as that between the exposure time and RH indicated significant and synergistic effects (P<0.05). The predictive model was validated by additional eight experiments and proven to be with good accuracy. Overall, this model established by the RSM could show the trend of the inactivation of spores, indicate the interactions between important factors, and provide a reference to determine effective conditions for the disinfection in different enclosed spaces by ClO2 gas. IMPLICATIONS The inactivation of indoor biological contaminants plays an important role in preventing the transmission of pathogens and ensuring human safety. The predictive model using response surface methodology indicates the influence and interaction of the main factors on the inactivation of Bacillus subtilis subsp. niger spores by ClO2 gas, and can predict a ClO2 gas treatment condition to achieve an effective sterilization of enclosed spaces. The results in this paper will provide a reference for the application of ClO2 gas treatments for indoor disinfection.
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Affiliation(s)
- Tao Wang
- a Institute of Medical Equipment, Academy of Military Medical Sciences , Tianjin , People's Republic of China
- b National Bio-protection Engineering Center , Tianjin , People's Republic of China
| | - Jiancheng Qi
- a Institute of Medical Equipment, Academy of Military Medical Sciences , Tianjin , People's Republic of China
- b National Bio-protection Engineering Center , Tianjin , People's Republic of China
| | - Jinhui Wu
- a Institute of Medical Equipment, Academy of Military Medical Sciences , Tianjin , People's Republic of China
- b National Bio-protection Engineering Center , Tianjin , People's Republic of China
| | - Limei Hao
- a Institute of Medical Equipment, Academy of Military Medical Sciences , Tianjin , People's Republic of China
- b National Bio-protection Engineering Center , Tianjin , People's Republic of China
| | - Ying Yi
- a Institute of Medical Equipment, Academy of Military Medical Sciences , Tianjin , People's Republic of China
- b National Bio-protection Engineering Center , Tianjin , People's Republic of China
| | - Song Lin
- a Institute of Medical Equipment, Academy of Military Medical Sciences , Tianjin , People's Republic of China
- b National Bio-protection Engineering Center , Tianjin , People's Republic of China
| | - Zongxing Zhang
- a Institute of Medical Equipment, Academy of Military Medical Sciences , Tianjin , People's Republic of China
- b National Bio-protection Engineering Center , Tianjin , People's Republic of China
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Shirasaki Y, Matsuura A, Uekusa M, Ito Y, Hayashi T. A study of the properties of chlorine dioxide gas as a fumigant. Exp Anim 2016; 65:303-10. [PMID: 27041456 PMCID: PMC4976244 DOI: 10.1538/expanim.15-0092] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Chlorine dioxide (ClO2) is a strong oxidant that possesses an antimicrobial activity. We demonstrated here that ClO2 gas is easily generated by mixing 3.35% sodium chlorite solution (Purogene) and 85% phosphoric acid at a 10:1 volume ratio without using an expensive machine. In a test room (87 m(3)), experiments were carried out using various amounts of sodium chlorite solution (0.25 ml/m(3) to 20.0 ml/m(3)). The gas concentration increased in a sodium chlorite volume-dependent manner and reached peak values of from 0.8 ppm to 40.8 ppm at 2 h-3 h, and then gradually decreased. No differences in gas concentrations were observed between 0.1 and 2.5 m above the floor, indicating that the gas was evenly distributed. Under high-humidity (approximately 80% relative humidity), colony formation of both Staphylococcus aureus and Escherichia coli was completely inhibited by ClO2 gas exposure at 1.0 ml/m(3) sodium chlorite solution (mean maximal concentration of 3.0 ppm). Exposure at 4.0 ml/m(3) sodium chlorite solution (mean maximal concentration of 10.6 ppm) achieved complete inactivation of Bacillus atrophaeus spores. In contrast, without humidification, the efficacy of ClO2 gas was apparently attenuated, suggesting that the atmospheric moisture is indispensable. Delicate electronic devices (computer, camera, etc.) operated normally, even after being subjected to more than 20 times of fumigation. Considering that our method for gas generation is simple, reproducible, and highly effective at decontaminating microbes, our approach is expected to serve as an inexpensive alternative method for cleaning and disinfecting animal facilities.
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Affiliation(s)
- Yasufumi Shirasaki
- Biological Research Department, Daiichi Sankyo RD Novare Co., Ltd., 1-16-13 Kita-Kasai, Edogawa-ku, Tokyo 134-8630, Japan
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Evaluation of the Efficacy of Methyl Bromide in the Decontamination of Building and Interior Materials Contaminated with Bacillus anthracis Spores. Appl Environ Microbiol 2016; 82:2003-2011. [PMID: 26801580 PMCID: PMC4807506 DOI: 10.1128/aem.03445-15] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Accepted: 01/08/2016] [Indexed: 12/03/2022] Open
Abstract
The primary goal of this study was to determine the conditions required for the effective inactivation of Bacillus anthracis spores on materials by using methyl bromide (MeBr) gas. Another objective was to obtain comparative decontamination efficacy data with three avirulent microorganisms to assess their potential for use as surrogates for B. anthracis Ames. Decontamination tests were conducted with spores of B. anthracis Ames and Geobacillus stearothermophilus, B. anthracis NNR1Δ1, and B. anthracis Sterne inoculated onto six different materials. Experimental variables included temperature, relative humidity (RH), MeBr concentration, and contact time. MeBr was found to be an effective decontaminant under a number of conditions. This study highlights the important role that RH has when fumigation is performed with MeBr. There were no tests in which a ≥6-log10 reduction (LR) of B. anthracis Ames was achieved on all materials when fumigation was done at 45% RH. At 75% RH, an increase in the temperature, the MeBr concentration, or contact time generally improved the efficacy of fumigation with MeBr. This study provides new information for the effective use of MeBr at temperatures and RH levels lower than those that have been recommended previously. The study also provides data to assist with the selection of an avirulent surrogate for B. anthracis Ames spores when additional tests with MeBr are conducted.
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Eichner A, Gollmer A, Späth A, Bäumler W, Regensburger J, König B, Maisch T. Fast and effective inactivation of Bacillus atrophaeus endospores using light-activated derivatives of vitamin B2. Photochem Photobiol Sci 2015; 14:387-96. [PMID: 25423452 DOI: 10.1039/c4pp00285g] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Highly resistant endospores may cause severe problems in medicine as well as in the food and packaging industries. We found that bacterial endospores can be inactivated quickly with reactive oxygen species (ROS) that were generated by a new generation of flavin photosensitizers. Flavins like the natural compound vitamin B2 are already known to produce ROS but they show a poor antimicrobial photodynamic killing efficacy due to the lack of positive charges. Therefore we synthesized new flavin photosensitizers that have one (FLASH-01a) or eight (FLASH-07a) positive charges and can hence attach to the negatively charged surface of endospores. In this study we used standardized Bacillus atrophaeus endospores (ATCC 9372) as a biological surrogate model for a proof-of-concept study of photodynamic inactivation experiments using FLASH-01a and FLASH-07a. After incubation of spores with different flavin concentrations, the flavin derivatives were excited with blue light at a light dose of 70 J cm(-2). The inactivation of spores was investigated either in suspension or after attachment to polyethylene terephthalate (PET) surfaces. Incubation of spores suspended in Millipore water with 4 mM FLASH-01a for 10 seconds and irradiation with blue light for 10 seconds caused a biologically relevant decrease of spore survival of 3.5 log10 orders. Using FLASH-07a under the same conditions we achieved a decrease of 4.4 log10 orders. Immobilized spores on PET surfaces were efficiently killed with 7.0 log10 orders using 8 mM FLASH-07a. The total treatment time (incubation + irradiation) was as short as 20 seconds. The results of this study show evidence that endospores can be fastly and effectively inactivated with new generations of flavin photosensitizers that may be useful for industrial or medical applications in the future.
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Affiliation(s)
- Anja Eichner
- Department of Dermatology, Regensburg University Hospital, 93053 Regensburg, Germany.
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Wood JP, Meyer KM, Kelly TJ, Choi YW, Rogers JV, Riggs KB, Willenberg ZJ. Environmental Persistence of Bacillus anthracis and Bacillus subtilis Spores. PLoS One 2015; 10:e0138083. [PMID: 26372011 PMCID: PMC4570822 DOI: 10.1371/journal.pone.0138083] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Accepted: 08/25/2015] [Indexed: 11/19/2022] Open
Abstract
There is a lack of data for how the viability of biological agents may degrade over time in different environments. In this study, experiments were conducted to determine the persistence of Bacillus anthracis and Bacillus subtilis spores on outdoor materials with and without exposure to simulated sunlight, using ultraviolet (UV)-A/B radiation. Spores were inoculated onto glass, wood, concrete, and topsoil and recovered after periods of 2, 14, 28, and 56 days. Recovery and inactivation kinetics for the two species were assessed for each surface material and UV exposure condition. Results suggest that with exposure to UV, decay of spore viability for both Bacillus species occurs in two phases, with an initial rapid decay, followed by a slower inactivation period. The exception was with topsoil, in which there was minimal loss of spore viability in soil over 56 days, with or without UV exposure. The greatest loss in viable spore recovery occurred on glass with UV exposure, with nearly a four log10 reduction after just two days. In most cases, B. subtilis had a slower rate of decay than B. anthracis, although less B. subtilis was recovered initially.
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Affiliation(s)
- Joseph P. Wood
- United States Environmental Protection Agency, Office of Research and Development, National Homeland Security Research Center, Research Triangle Park, North Carolina, United States of America
- * E-mail:
| | - Kathryn M. Meyer
- Oak Ridge Institute for Science and Education, Research Triangle Park, NC, United States of America
| | - Thomas J. Kelly
- Battelle Memorial Institute, Columbus, Ohio, United States of America
| | - Young W. Choi
- Battelle Memorial Institute, Columbus, Ohio, United States of America
| | - James V. Rogers
- Battelle Memorial Institute, Columbus, Ohio, United States of America
| | - Karen B. Riggs
- Battelle Memorial Institute, Columbus, Ohio, United States of America
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Pinho SC, Nunes OC, Lobo-da-Cunha A, Almeida MF. Inactivation of Geobacillus stearothermophilus spores by alkaline hydrolysis applied to medical waste treatment. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2015; 161:51-56. [PMID: 26150372 DOI: 10.1016/j.jenvman.2015.06.045] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Revised: 06/19/2015] [Accepted: 06/23/2015] [Indexed: 06/04/2023]
Abstract
Although alkaline hydrolysis treatment emerges as an alternative disinfection/sterilization method for medical waste, information on its effects on the inactivation of biological indicators is scarce. The effects of alkaline treatment on the resistance of Geobacillus stearothermophilus spores were investigated and the influence of temperature (80 °C, 100 °C and 110 °C) and NaOH concentration was evaluated. In addition, spore inactivation in the presence of animal tissues and discarded medical components, used as surrogate of medical waste, was also assessed. The effectiveness of the alkaline treatment was carried out by determination of survival curves and D-values. No significant differences were seen in D-values obtained at 80 °C and 100 °C for NaOH concentrations of 0.5 M and 0.75 M. The D-values obtained at 110 °C (2.3-0.5 min) were approximately 3 times lower than those at 100 °C (8.8-1.6 min). Independent of the presence of animal tissues and discarded medical components, 6 log10 reduction times varied between 66 and 5 min at 100 °C-0.1 M NaOH and 110 °C-1 M NaOH, respectively. The alkaline treatment may be used in future as a disinfection or sterilization alternative method for contaminated waste.
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Affiliation(s)
- Sílvia C Pinho
- LEPABE, Department of Metallurgical and Materials Engineering, Faculty of Engineering, University of Porto, Portugal.
| | - Olga C Nunes
- LEPABE, Department of Chemical Engineering, Faculty of Engineering, University of Porto, Portugal
| | - Alexandre Lobo-da-Cunha
- Department of Microscopy, Institute of Biomedical Sciences Abel Salazar (ICBAS), University of Porto, Portugal
| | - Manuel F Almeida
- LEPABE, Department of Metallurgical and Materials Engineering, Faculty of Engineering, University of Porto, Portugal
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Omotade TO, Bernhards RC, Klimko CP, Matthews ME, Hill AJ, Hunter MS, Webster WM, Bozue JA, Welkos SL, Cote CK. The impact of inducing germination of Bacillus anthracis and Bacillus thuringiensis spores on potential secondary decontamination strategies. J Appl Microbiol 2014; 117:1614-33. [PMID: 25196092 DOI: 10.1111/jam.12644] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Revised: 09/03/2014] [Accepted: 09/03/2014] [Indexed: 12/22/2022]
Abstract
AIMS Decontamination and remediation of a site contaminated by the accidental or intentional release of fully virulent Bacillus anthracis spores are difficult, costly and potentially damaging to the environment. Development of novel decontamination strategies that have minimal environmental impacts remains a high priority. Although ungerminated spores are amongst the most resilient organisms known, once exposed to germinants, the germinating spores, in some cases, become susceptible to antimicrobial environments. We evaluated the concept that once germinated, B. anthracis spores would be less hazardous and significantly easier to remediate than ungerminated dormant spores. METHODS AND RESULTS Through in vitro germination and sensitivity assays, we demonstrated that upon germination, B. anthracis Ames spores and Bacillus thuringiensis Al Hakam spores (serving as a surrogate for B. anthracis) become susceptible to environmental stressors. The majority of these germinated B. anthracis and B. thuringiensis spores were nonviable after exposure to a defined minimal germination-inducing solution for prolonged periods of time. Additionally, we examined the impact of potential secondary disinfectant strategies including bleach, hydrogen peroxide, formaldehyde and artificial UV-A, UV-B and UV-C radiation, employed after a 60-min germination-induction step. Each secondary disinfectant employs a unique mechanism of killing; as a result, germination-induction strategies are better suited for some secondary disinfectants than others. CONCLUSIONS These results provide evidence that the deployment of an optimal combination strategy of germination-induction/secondary disinfection may be a promising aspect of wide-area decontamination following a B. anthracis contamination event. SIGNIFICANCE AND IMPACT OF THE STUDY By inducing spores to germinate, our data confirm that the resulting cells exhibit sensitivities that can be leveraged when paired with certain decontamination measures. This increased susceptibility could be exploited to devise more efficient and safe decontamination measures and may obviate the need for more stringent methods that are currently in place.
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Affiliation(s)
- T O Omotade
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, MD, USA
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Kaspari O, Lemmer K, Becker S, Lochau P, Howaldt S, Nattermann H, Grunow R. Decontamination of a BSL3 laboratory by hydrogen peroxide fumigation using three different surrogates for Bacillus anthracis spores. J Appl Microbiol 2014; 117:1095-103. [PMID: 25040253 DOI: 10.1111/jam.12601] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2014] [Revised: 07/08/2014] [Accepted: 07/15/2014] [Indexed: 11/29/2022]
Abstract
AIMS Two independent trials investigated the decontamination of a BSL3 laboratory using vaporous hydrogen peroxide and compared the effect on spores of Bacillus cereus, Bacillus subtilis and Bacillus thuringiensis as surrogates for Bacillus anthracis spores, while spores of Geobacillus stearothermophilus served as control. METHODS AND RESULTS Carriers containing 1·0 × 10(6) spores were placed at various locations within the laboratory before fumigation with hydrogen peroxide following a previously validated protocol. Afterwards, carriers were monitored by plating out samples on agar and observing enrichment in nutrient medium for up to 14 days. Three months later, the experiment was repeated and results were compared. On 98 of 102 carriers, no viable spores could be detected after decontamination, while the remaining four carriers exhibited growth of CFU only after enrichment for several days. Reduction factors between 4·0 and 6·0 log levels could be reached. CONCLUSIONS A validated decontamination of a laboratory with hydrogen peroxide represents an effective alternative to fumigation with formaldehyde. Spores of B. cereus seem to be more resistant than those of G. stearothermophilus. SIGNIFICANCE AND IMPACT OF THE STUDY The results of this study provide important results in the field of hydrogen peroxide decontamination when analysing the effect on spores other than those of G. stearothermophilus.
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Affiliation(s)
- O Kaspari
- Division Highly Pathogenic Microorganisms, Centre for Biological Threats and Special Pathogens, Robert Koch-Institute, Berlin, Germany
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Ryan SP, Lee SD, Calfee MW, Wood JP, McDonald S, Clayton M, Griffin-Gatchalian N, Touati A, Smith L, Nysewander M. Effect of inoculation method on the determination of decontamination efficacy against Bacillus spores. World J Microbiol Biotechnol 2014; 30:2609-23. [PMID: 24928258 PMCID: PMC4150995 DOI: 10.1007/s11274-014-1684-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Accepted: 06/03/2014] [Indexed: 11/27/2022]
Abstract
Decontamination studies investigating the effectiveness of products and processes for the inactivation of Bacillus species spores have traditionally utilized metering viable spores in a liquid suspension onto test materials (coupons). The current study addresses the representativeness of studies using this type of inoculation method compared to when coupons are dosed with a metered amount of aerosolized spores. The understanding of this comparability is important in order to assess the representativeness of such laboratory-based testing when deciding upon decontamination options for use against Bacillus anthracis spores. Temporal inactivation of B. anthracis surrogate (B. subtilis) spores on representative materials using fumigation with chlorine dioxide, spraying of a pH-adjusted bleach solution, or immersion in the solution was investigated as a function of inoculation method (liquid suspension or aerosol dosing). Results indicated that effectiveness, measured as log reduction, was statistically significantly lower when liquid inoculation was used for some material and decontaminant combinations. Differences were mostly noted for the materials observed to be more difficult to decontaminate (i.e., wood and carpet). Significant differences in measured effectiveness were also noted to be a function of the pH-adjusted bleach application method used in the testing (spray or immersion). Based upon this work and the cited literature, it is clear that inoculation method, decontaminant application method, and handling of non-detects (i.e., or detection limits) can have an impact on the sporicidal efficacy measurements.
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Affiliation(s)
- Shawn P Ryan
- US EPA, Office of Research and Development, National Homeland Security Research Center, MD E343-06; 109 TW Alexander Dr., Research Triangle Park, NC, 27711, USA,
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Wendling MQS, Lastivka AT, Rogers JV. Inactivation of Bacillus AnthracisSpores on All-Weather Paper. APPLIED BIOSAFETY 2013. [DOI: 10.1177/153567601301800305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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34
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Calfee MW, Lee SD, Ryan SP. A rapid and repeatable method to deposit bioaerosols on material surfaces. J Microbiol Methods 2013; 92:375-80. [PMID: 23384827 DOI: 10.1016/j.mimet.2013.01.015] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Revised: 01/14/2013] [Accepted: 01/14/2013] [Indexed: 11/28/2022]
Abstract
A simple method for repeatably inoculating surfaces with a precise quantity of aerosolized spores was developed. Laboratory studies were conducted to evaluate the variability of the method within and between experiments, the spatial distribution of spore deposition, the applicability of the method to complex surface types, and the relationship between material surface roughness and spore recoveries. Surface concentrations, as estimated by recoveries from wetted-wipe sampling, were between 5×10(3) and 1.5×10(4)CFUcm(-2) across the entire area (930cm(2)) inoculated. Between-test variability (Cv) in spore recoveries was 40%, 81%, 66%, and 20% for stainless steel, concrete, wood, and drywall, respectively. Within-test variability was lower, and did not exceed 33%, 47%, 52%, and 20% for these materials. The data demonstrate that this method is repeatable, is effective at depositing spores across a target surface area, and can be used to dose complex materials such as concrete, wood, and drywall. In addition, the data demonstrate that surface sampling recoveries vary by material type, and this variability can partially be explained by the material surface roughness index. This deposition method was developed for use in biological agent detection, sampling, and decontamination studies, however, is potentially beneficial to any scientific discipline that investigates surfaces containing aerosol-borne particles.
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Affiliation(s)
- M Worth Calfee
- US EPA, Office of Research and Development, National Homeland Security Research Center, Research Triangle Park, NC, USA.
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35
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Lowe JJ, Gibbs SG, Iwen PC, Smith PW, Hewlett AL. Decontamination of a hospital room using gaseous chlorine dioxide: Bacillus anthracis, Francisella tularensis, and Yersinia pestis. JOURNAL OF OCCUPATIONAL AND ENVIRONMENTAL HYGIENE 2013; 10:533-539. [PMID: 23971883 DOI: 10.1080/15459624.2013.818241] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
This study assessed the efficacy of gaseous chlorine dioxide for inactivation of Bacillus anthracis, Francisella tularensis, and Yersinia pestis in a hospital patient care suite. Spore and vegetative cells of Bacillus anthracis Sterne 34F2, spores of Bacillus atrophaeus ATCC 9372 and vegetative cells of both Francisella tularensis ATCC 6223 and Yersinia pestis A1122 were exposed to gaseous chlorine dioxide in a patient care suite. Organism inactivation was then assessed by log reduction in viable organisms postexposure to chlorine dioxide gas compared to non-exposed control organism. Hospital room decontamination protocols utilizing chlorine dioxide gas concentrations of 377 to 385 ppm maintained to exposures of 767 ppm-hours with 65% relative humidity consistently achieved complete inactivation of B. anthracis and B. atrophaeus spores, as well as vegetative cells of B. anthracis, F. tularensis, and Y. pestis. Decrease in exposure (ppm-hours) and relative humidity (<65%) or restricting airflow reduced inactivation but achieved >8 log reductions in organisms. Up to 10-log reductions were achieved in a hospital room with limited impact on adjacent areas, indicating chlorine dioxide concentrations needed for decontamination of highly concentrated (>6 logs) organisms can be achieved throughout a hospital room. This study translates laboratory chlorine dioxide fumigation studies applied in a complex clinical environment.
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Affiliation(s)
- John J Lowe
- a Department of Environmental, Agricultural & Occupational Health , University of Nebraska Medical Center College of Public Health , Omaha , Nebraska
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Fox JM, Shuttleworth G, Martin F. Methodology to reduce formaldehyde exposure during laboratory fumigation. INTERNATIONAL JOURNAL OF ENVIRONMENTAL HEALTH RESEARCH 2012; 23:400-406. [PMID: 23163567 DOI: 10.1080/09603123.2012.743114] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Laboratory fumigations achieve disinfection and are performed following the non-contained release of infectious agents. Gaseous formaldehyde remains the most commonly used fumigant but evidence relates formaldehyde exposure to the development of nasopharyngeal cancer. Laboratory personnel must be confident and competent in the procedure to protect themselves, others and the environment. The present study outlines methodology to reduce worker exposure to formaldehyde during essential fumigation training. A simulation fumigation protocol significantly shorter than a genuine fumigation was devised using aromatic cajuput oil to train staff in the fumigation technique without potentially harmful exposure to formaldehyde. Personnel reported increased confidence and compliance of the fumigation procedure after the simulation suggesting that this model protocol would be a valuable training tool for any individual that may be required to undertake genuine formaldehyde fumigations.
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Affiliation(s)
- James Martin Fox
- a Centre for Immunology and Infection, Department of Biology and Hull York Medical School , Wentworth Way, Heslington, University of York , York , UK
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Li YJ, Zhu N, Jia HQ, Wu JH, Yi Y, Qi JC. Decontamination of Bacillus subtilis var. niger spores on selected surfaces by chlorine dioxide gas. J Zhejiang Univ Sci B 2012; 13:254-60. [PMID: 22467366 DOI: 10.1631/jzus.b1100289] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE Chlorine dioxide (CD) gas has been used as a fumigant in the disinfection of biosafety laboratories. In this study, some experiments were conducted to assess the inactivation of spores inoculated on six materials [stainless steel (SS), painted steel (PS), polyvinyl chlorid (PVC), polyurethane (PU), glass (GS), and cotton cloth (CC)] by CD gas. The main aims of the study were to determine the sporicidal efficacy of CD gas and the effect of prehumidification before decontamination on sporicidal efficacy. METHODS Material coupons (1.2 cm diameter of SS, PS, and PU; 1.0 cm×1.0 cm for PVC, GS, and CC) were contaminated with 10 μl of Bacillus subtilis var. niger (ATCC 9372) spore suspension in mixed organic burden and then dried in a biosafety cabinet for 12 h. The spores were recovered by soaking the coupons in 5 ml of extraction liquid for 1 h and then vortexing the liquid for 1 min. RESULTS The log reductions in spore numbers on inoculated test materials exposed to CD gas [0.080% (volume ratio, v/v) for 3 h] were in the range of from 1.80 to 6.64. Statistically significant differences were found in decontamination efficacies on test material coupons of SS, PS, PU, and CC between with and without a 1-h prehumidification treatment. With the extraction method, there were no statistically significant differences in the recovery ratios between the porous and non-porous materials. CONCLUSIONS The results reported from this study could provide information for developing decontamination technology based on CD gas for targeting surface microbial contamination.
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Affiliation(s)
- Yan-ju Li
- School of Environmental Science and Engineering, Tianjin University, Tianjin 300072, China.
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38
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Worth Calfee M, Wendling M. The effects of environmental conditions on persistence and inactivation of Brucella suis on building material surfaces. Lett Appl Microbiol 2012; 54:504-10. [DOI: 10.1111/j.1472-765x.2012.03237.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Campbell CG, Kirvel RD, Love AH, Bailey CG, Miles R, Schweickert J, Sutton M, Raber E. Decontamination After a Release ofB. anthracisSpores. Biosecur Bioterror 2012; 10:108-22. [DOI: 10.1089/bsp.2011.0095] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Chris G. Campbell
- Chris G. Campbell, PhD, is an Environmental Scientist; Robert D. Kirvel, PhD, is a science writer; Christopher G. Bailey, PhD, is a scientist in the Biosciences and Biotechnology Division; Robin Miles, MSME, MBA, is Group Leader for the Center for Micro and Nano Technology; Jerry Schweickert, MPH, is an Environmental Scientist; Mark Sutton, PhD, is a scientist in the Chemical Sciences Division; and Ellen Raber, MS, is Deputy Program Director for Counterterrorism in the Global Security Principal
| | - Robert D. Kirvel
- Chris G. Campbell, PhD, is an Environmental Scientist; Robert D. Kirvel, PhD, is a science writer; Christopher G. Bailey, PhD, is a scientist in the Biosciences and Biotechnology Division; Robin Miles, MSME, MBA, is Group Leader for the Center for Micro and Nano Technology; Jerry Schweickert, MPH, is an Environmental Scientist; Mark Sutton, PhD, is a scientist in the Chemical Sciences Division; and Ellen Raber, MS, is Deputy Program Director for Counterterrorism in the Global Security Principal
| | - Adam H. Love
- Chris G. Campbell, PhD, is an Environmental Scientist; Robert D. Kirvel, PhD, is a science writer; Christopher G. Bailey, PhD, is a scientist in the Biosciences and Biotechnology Division; Robin Miles, MSME, MBA, is Group Leader for the Center for Micro and Nano Technology; Jerry Schweickert, MPH, is an Environmental Scientist; Mark Sutton, PhD, is a scientist in the Chemical Sciences Division; and Ellen Raber, MS, is Deputy Program Director for Counterterrorism in the Global Security Principal
| | - Christopher G. Bailey
- Chris G. Campbell, PhD, is an Environmental Scientist; Robert D. Kirvel, PhD, is a science writer; Christopher G. Bailey, PhD, is a scientist in the Biosciences and Biotechnology Division; Robin Miles, MSME, MBA, is Group Leader for the Center for Micro and Nano Technology; Jerry Schweickert, MPH, is an Environmental Scientist; Mark Sutton, PhD, is a scientist in the Chemical Sciences Division; and Ellen Raber, MS, is Deputy Program Director for Counterterrorism in the Global Security Principal
| | - Robin Miles
- Chris G. Campbell, PhD, is an Environmental Scientist; Robert D. Kirvel, PhD, is a science writer; Christopher G. Bailey, PhD, is a scientist in the Biosciences and Biotechnology Division; Robin Miles, MSME, MBA, is Group Leader for the Center for Micro and Nano Technology; Jerry Schweickert, MPH, is an Environmental Scientist; Mark Sutton, PhD, is a scientist in the Chemical Sciences Division; and Ellen Raber, MS, is Deputy Program Director for Counterterrorism in the Global Security Principal
| | - Jerry Schweickert
- Chris G. Campbell, PhD, is an Environmental Scientist; Robert D. Kirvel, PhD, is a science writer; Christopher G. Bailey, PhD, is a scientist in the Biosciences and Biotechnology Division; Robin Miles, MSME, MBA, is Group Leader for the Center for Micro and Nano Technology; Jerry Schweickert, MPH, is an Environmental Scientist; Mark Sutton, PhD, is a scientist in the Chemical Sciences Division; and Ellen Raber, MS, is Deputy Program Director for Counterterrorism in the Global Security Principal
| | - Mark Sutton
- Chris G. Campbell, PhD, is an Environmental Scientist; Robert D. Kirvel, PhD, is a science writer; Christopher G. Bailey, PhD, is a scientist in the Biosciences and Biotechnology Division; Robin Miles, MSME, MBA, is Group Leader for the Center for Micro and Nano Technology; Jerry Schweickert, MPH, is an Environmental Scientist; Mark Sutton, PhD, is a scientist in the Chemical Sciences Division; and Ellen Raber, MS, is Deputy Program Director for Counterterrorism in the Global Security Principal
| | - Ellen Raber
- Chris G. Campbell, PhD, is an Environmental Scientist; Robert D. Kirvel, PhD, is a science writer; Christopher G. Bailey, PhD, is a scientist in the Biosciences and Biotechnology Division; Robin Miles, MSME, MBA, is Group Leader for the Center for Micro and Nano Technology; Jerry Schweickert, MPH, is an Environmental Scientist; Mark Sutton, PhD, is a scientist in the Chemical Sciences Division; and Ellen Raber, MS, is Deputy Program Director for Counterterrorism in the Global Security Principal
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Gordon D, Carruthers BA, Theriault S. Gaseous Decontamination Methods in High-containment Laboratories. APPLIED BIOSAFETY 2012. [DOI: 10.1177/153567601201700107] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Diane Gordon
- Public Health Agency of Canada, Winnipeg, Manitoba, Canada
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Possible overestimation of surface disinfection efficiency by assessment methods based on liquid sampling procedures as demonstrated by in situ quantification of spore viability. Appl Environ Microbiol 2011; 77:6208-14. [PMID: 21742922 DOI: 10.1128/aem.00649-11] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The standard test methods used to assess the efficiency of a disinfectant applied to surfaces are often based on counting the microbial survivors sampled in a liquid, but total cell removal from surfaces is seldom achieved. One might therefore wonder whether evaluations of microbial survivors in liquid-sampled cells are representative of the levels of survivors in whole populations. The present study was thus designed to determine the "damaged/undamaged" status induced by a peracetic acid disinfection for Bacillus atrophaeus spores deposited on glass coupons directly on this substrate and to compare it to the status of spores collected in liquid by a sampling procedure. The method utilized to assess the viability of both surface-associated and liquid-sampled spores included fluorescence labeling with a combination of Syto 61 and Chemchrome V6 dyes and quantifications by analyzing the images acquired by confocal laser scanning microscopy. The principal result of the study was that the viability of spores sampled in the liquid was found to be poorer than that of surface-associated spores. For example, after 2 min of peracetic acid disinfection, less than 17% ± 5% of viable cells were detected among liquid-sampled cells compared to 79% ± 5% or 47% ± 4%, respectively, when the viability was evaluated on the surface after or without the sampling procedure. Moreover, assessments of the survivors collected in the liquid phase, evaluated using the microscopic method and standard plate counts, were well correlated. Evaluations based on the determination of survivors among the liquid-sampled cells can thus overestimate the efficiency of surface disinfection procedures.
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Gordon D, Madden B, Krishnan J, Klassen S, Dalmasso J, Theriault S. Implications of paper vs stainless steel biological indicator substrates for formaldehyde gas decontamination. J Appl Microbiol 2010; 110:455-62. [PMID: 21114595 DOI: 10.1111/j.1365-2672.2010.04899.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIMS This study was undertaken to determine the effectiveness of biological indicators currently being employed during formaldehyde decontamination. Data suggest that detectable amounts of formaldehyde are absorbed into the paper strips contained in currently used biological indicators. Absorbed formaldehyde has the potential to inhibit the growth of indicator spores, thus leading to false negative results. Indicators composed of either stainless steel carriers or paper strips were investigated to determine whether stainless steel carriers can be used as an alternative to paper strip indicators. METHODS AND RESULTS Biological indicators were exposed to formaldehyde gas and were tested for the presence of formaldehyde and any possible inhibition of spore growth. Absorbed formaldehyde was detected in the paper strip carriers while no formaldehyde was detected from any of the stainless steel carriers. Exposed paper strips were found to inhibit growth of up to 1 × 10(6) spores while the stainless steel carriers did not inhibit the growth of spores. CONCLUSIONS During decontamination, biological indicators composed of paper spore strips absorb formaldehyde and inhibit growth of any surviving spores. Stainless steel carriers do not absorb formaldehyde and are an ideal alternative substrate for biological indicators. SIGNIFICANCE AND IMPACT OF THE STUDY The popular paper strip biological indicator can lead to false negative results during decontamination and is unsuitable for validating formaldehyde decontamination.
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Affiliation(s)
- D Gordon
- Public Health Agency of Canada, National Microbiology Laboratory, Winnipeg, MB, Canada
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Maillard JY. Innate resistance to sporicides and potential failure to decontaminate. J Hosp Infect 2010; 77:204-9. [PMID: 20850897 DOI: 10.1016/j.jhin.2010.06.028] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2010] [Accepted: 06/23/2010] [Indexed: 12/22/2022]
Abstract
Bacterial spores are frequently intrinsically resistant to biocides and only a number of alkylating and oxidising biocides are sporicidal under certain conditions. Activity against spores is affected by several key factors such as concentration, exposure time, soiling, and the types of surface to be treated. Sporicidal efficacy is usually achieved after an exposure time of several minutes with a high concentration of a biocide. Failure to understand these factors will result in decreased sporicide activity and spore survival. Sporicides in healthcare settings are used for surface disinfection and for the high level disinfection of certain medical devices (e.g. endoscopes). With efficacy data in mind, sporicidal activity should be achieved for the disinfection of medical devices where both high concentration and long exposure time occur. However, for the disinfection of environmental surfaces, high concentration is not recommended, nor is long exposure time achievable. In this case, sporicidal activity is severely reduced and spore survival following treatment is to be expected and contributes to the explanation of spore persistence on surfaces.
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Affiliation(s)
- J-Y Maillard
- Welsh School of Pharmacy, Cardiff University, Cardiff, UK.
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Grand I, Bellon-Fontaine MN, Herry JM, Hilaire D, Moriconi FX, Naïtali M. The resistance of Bacillus atrophaeus spores to the bactericidal activity of peracetic acid is influenced by both the nature of the solid substrates and the mode of contamination. J Appl Microbiol 2010; 109:1706-14. [PMID: 20618887 DOI: 10.1111/j.1365-2672.2010.04799.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
AIMS To evaluate the impact of the mode of contamination in relation with the nature of solid substrates on the resistance of spores of Bacillus atrophaeus -selected as surrogates of Bacillus anthracis- to a disinfectant, peracetic acid. METHODS AND RESULTS Six materials confronted in urban and military environments were selected for their different structural and physicochemical properties. In parallel, two modes of contamination were examined, i.e. deposition and immersion. Deposition was used to simulate contamination by an aerosol and immersion by an extended contact with liquids. A pronounced difference in the biocontamination levels and spatial organization of spores was observed depending on the mode of contamination and the nature of the solid substrate considered, with consequences on decontamination. Contamination by immersion led to lower efficiency of peracetic acid decontamination than contamination by deposition. Infiltration of spores into porous materials after immersion is one reason. In contrast, the deposition mode aggregates cells at the surface of materials, explaining the similar disinfecting behaviour of porous and nonporous substrates when considering this inoculation route. CONCLUSIONS The inoculation route was shown to be as influential a parameter as material characteristics (porosity and wettability) for decontamination efficacy. SIGNIFICANCE AND IMPACT OF THE STUDY These results provide comparative information for the decontamination of B. atrophaeus spores in function of the mode of contamination and the nature of solid substrates.
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Affiliation(s)
- I Grand
- AgroParisTech, UMR 1319 Micalis, Equipe B2HM, Massy, France
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Richter WR, Wendling MQS, Rogers JV. A Novel Approach for Conducting Room-scale Vaporous Hydrogen Peroxide Decontamination of VirulentBacillus AnthracisSpores. APPLIED BIOSAFETY 2009. [DOI: 10.1177/153567600901400403] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Rogers JV, Richter WR, Shaw MQ, Shesky AM. Large-Scale Inactivation ofBacillus AnthracisAmes, Vollum, and Sterne Spores Using Vaporous Hydrogen Peroxide. APPLIED BIOSAFETY 2009. [DOI: 10.1177/153567600901400304] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Rogers JV, Richter WR, Shaw MQ, Choi YW. Vapour-phase hydrogen peroxide inactivates Yersinia pestis dried on polymers, steel, and glass surfaces. Lett Appl Microbiol 2009; 47:279-85. [PMID: 19241520 DOI: 10.1111/j.1472-765x.2008.02421.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIMS This study evaluated the inactivation of virulent Yersinia pestis dried on polymers, steel, and glass surfaces using vapour-phase hydrogen peroxide. METHODS AND RESULTS A suspension of Y. pestis CO92 (1.70 x 10(8) CFU) was dried on 10 different types of test surfaces and exposed to vapour-phase hydrogen peroxide fumigation for a contact time of 2 h. A significant reduction in the log10 CFU of Y. pestis on all 10 materials was observed between the controls evaluated after a 1 h drying time and unexposed controls evaluated after the decontamination run. Qualitative growth assessment showed that vapour-phase hydrogen peroxide exposure inactivated Y. pestis on all replicates of the 10 test materials as well as biological indicators up to 7 days postexposure. CONCLUSIONS Virulent Y. pestis CO92 is inactivated on polymers, steel, and glass surfaces when exposed to vapour-phase hydrogen peroxide without observable physical damage to the test materials. SIGNIFICANCE AND IMPACT OF THE STUDY This study provides information for using vapour-phase hydrogen peroxide as a practical process for the decontamination of virulent Y. pestis in circumstances where time-dependent attenuation/inactivation orliquid/heat decontamination may not be the most suitable approach.
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Affiliation(s)
- J V Rogers
- Battelle Biomedical Research Center, 505 King Avenue, JM-7, Columbus, OH 43201, USA.
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Heninger SJ, Anderson CA, Beltz G, Onderdonk AB. Decontamination ofBacillus anthracisSpores: Evaluation of Various Disinfectants. APPLIED BIOSAFETY 2009; 14:7-10. [PMID: 20967138 DOI: 10.1177/153567600901400103] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Rogers J, Richter W, Choi Y, Judd A. Use of superabsorbent polymer gels for surface decontamination ofBacillus anthracisspores. Lett Appl Microbiol 2009; 48:180-6. [DOI: 10.1111/j.1472-765x.2008.02506.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Rogers JV, Choi YW, Richter WR, Stone HJ, Taylor ML. Bacillus AnthracisSpore Inactivation by Fumigant Decontamination. APPLIED BIOSAFETY 2008. [DOI: 10.1177/153567600801300203] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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