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Nelson S, Hofacre K, Shah S, Silvestri E, Gallardo V, Mikelonis A, James R, Calfee MW. Evaluation of sample processing methods to improve the detection of Bacillus anthracis in difficult sample matrices. ENVIRONMENTAL MONITORING AND ASSESSMENT 2022; 194:789. [PMID: 36104633 PMCID: PMC10410253 DOI: 10.1007/s10661-022-10467-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Accepted: 09/10/2022] [Indexed: 06/15/2023]
Abstract
Large area sampling approaches have been developed and implemented by the US Environmental Protection Agency (EPA) to increase sample sizes, and potentially representativeness, in outdoor urban environments (e.g., concrete, asphalt, grass/landscaping). These sampling approaches could be implemented in response to an outdoor biological contamination incident or bioterrorism attack to determine the extent of contamination and for clearance following remediation. However, sample collection over large areas often contains an extensive amount of co-collected debris and native background microorganisms that interfere with the detection of biological threat agents. Sample processing methods that utilize basic laboratory equipment amenable to field deployment were selected and applied to turbid aqueous samples (TAS) to reduce particulates and native environmental organisms prior to culture and rapid viability-polymerase chain reaction (RV-PCR) analytical methods. Bacillus anthracis Sterne (BaS) spores were spiked into TAS collected by soil grab, wet vacuum collection from an outdoor concrete surface, or storm water runoff from an urban parking lot. The implementation of a sample processing method improved the sensitivity of culture and RV-PCR analytical methods for BaS spore detection in soil and wet vacuum TAS samples compared to baseline (minimal to no field processing methods applied). For soil, when the processing method was applied, samples with 15 colony forming units (CFU)/ml (60 CFU/g) and 1.5 CFU/mL (6 CFU/g) BaS spore load were detected using culture and RV-PCR, respectively. Most notably, the processing methods greatly improved the sensitivity of the RV-PCR analytical method for the wet vacuum TAS from no detection at the 1500 CFU/mL BaS spore load level to as low as 1.5 CFU/mL BaS spore load.
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Affiliation(s)
- Scott Nelson
- Battelle Memorial Institute, King Avenue, Columbus, OH, USA
| | - Kent Hofacre
- Battelle Memorial Institute, King Avenue, Columbus, OH, USA
| | - Sanjiv Shah
- U.S. Environmental Protection Agency, Pennsylvania Avenue, Washington, DC, USA
| | - Erin Silvestri
- U.S. Environmental Protection Agency, Martin Luther King Drive, Cincinnati, OH, USA
| | - Vicente Gallardo
- U.S. Environmental Protection Agency, Martin Luther King Drive, Cincinnati, OH, USA
| | - Anne Mikelonis
- U.S. Environmental Protection Agency, 109 TW Alexander Drive, Durham, NC, 27711, USA
| | - Ryan James
- Battelle Memorial Institute, King Avenue, Columbus, OH, USA
| | - M Worth Calfee
- U.S. Environmental Protection Agency, 109 TW Alexander Drive, Durham, NC, 27711, USA.
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Wang D, Chen G, Lyu Y, Feng E, Zhu L, Pan C, Zhang W, Liu X, Wang H. A CRISPR/Cas12a-based DNAzyme visualization system for rapid, non-electrically dependent detection of Bacillus anthracis. Emerg Microbes Infect 2021; 11:428-437. [PMID: 34842509 PMCID: PMC8812752 DOI: 10.1080/22221751.2021.2012091] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
As next-generation pathogen detection methods, CRISPR-Cas-based detection methods can perform single-nucleotide polymorphism (SNP) level detection with high sensitivity and good specificity. They do not require any particular equipment, which opens up new possibilities for the accurate detection and identification of Bacillus anthracis. In this study, we developed a complete detection system for B. anthracis based on Cas12a. We used two chromosomally located SNP targets and two plasmid targets to identify B. anthracis with high accuracy. The CR5 target is completely new. The entire detection process can be completed within 90 min without electrical power and with single-copy level sensitivity. We also developed an unaided-eye visualization system based on G4-DNAzyme for use with our CRISPR-Cas12a detection system. This visualization system has good prospects for deployment in field-based point-of-care detection. We used the antisense nucleic acid CatG4R as the detection probe, which showed stronger resistance to interference from components of the solution. CatG4R can also be designed as an RNA molecule for adaptation to Cas13a detection, thereby broadening the scope of the detection system.
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Affiliation(s)
- Dongshu Wang
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Biotechnology, Beijing 100071, China
| | - Gang Chen
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Biotechnology, Beijing 100071, China
| | - Yufei Lyu
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Biotechnology, Beijing 100071, China
| | - Erling Feng
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Biotechnology, Beijing 100071, China
| | - Li Zhu
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Biotechnology, Beijing 100071, China
| | - Chao Pan
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Biotechnology, Beijing 100071, China
| | - Weicai Zhang
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Biotechnology, Beijing 100071, China
| | - Xiankai Liu
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Biotechnology, Beijing 100071, China
| | - Hengliang Wang
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Biotechnology, Beijing 100071, China
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3
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Rohde A, Papp S, Feige P, Grunow R, Kaspari O. Development of a novel selective agar for the isolation and detection of Bacillus anthracis. J Appl Microbiol 2020; 129:311-318. [PMID: 32052540 DOI: 10.1111/jam.14615] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 01/30/2020] [Accepted: 02/11/2020] [Indexed: 11/27/2022]
Abstract
AIMS The aim of this study was to develop a novel selective agar for the specific isolation and detection of Bacillus anthracis. METHODS AND RESULTS Based on published data on antibiotic resistance and susceptibility of B. anthracis and other closely related species of the Bacillus cereus sensu lato group, a new selective agar formulation termed CEFOMA (Bacillus CEreus sensu lato group-specific antibiotics, FOsfomycin, MAcrolides) was developed and evaluated. All tested strains of B. anthracis were able to grow on CEFOMA with the same colony number as on non-selective media, whereas CEFOMA inhibited the growth of the other species within the B. cereus sensu lato group. In comparison to other selective agars, CEFOMA had a superior performance and considerably reduced the total amount of accompanying flora in soil. Furthermore, B. anthracis was successfully isolated from deliberately spiked soil samples. CONCLUSIONS CEFOMA is a highly promising selective agar for the efficient isolation of B. anthracis from environmental samples with a large bacterial background flora. SIGNIFICANCE AND IMPACT OF THE STUDY The isolation of B. anthracis from environmental samples is severely impaired by the lack of adequate selective agars which suppress the growth of other bacteria. CEFOMA agar represents an important improvement and suitable alternative to currently used selective agars.
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Affiliation(s)
- A Rohde
- Highly Pathogenic Microorganisms (ZBS 2), Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
| | - S Papp
- Highly Pathogenic Microorganisms (ZBS 2), Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
| | - P Feige
- Highly Pathogenic Microorganisms (ZBS 2), Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
| | - R Grunow
- Highly Pathogenic Microorganisms (ZBS 2), Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
| | - O Kaspari
- Highly Pathogenic Microorganisms (ZBS 2), Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
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4
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Zhang Y, Mathys A. Superdormant Spores as a Hurdle for Gentle Germination-Inactivation Based Spore Control Strategies. Front Microbiol 2019; 9:3163. [PMID: 30662433 PMCID: PMC6328458 DOI: 10.3389/fmicb.2018.03163] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Accepted: 12/06/2018] [Indexed: 02/04/2023] Open
Abstract
Bacterial spore control strategies based on the germination-inactivation principle can lower the thermal load needed to inactivate bacterial spores and thus preserve food quality better. However, the success of this strategy highly depends on the germination of spores, and a subpopulation of spores that fail to germinate or germinate extremely slowly hinders the application of this strategy. This subpopulation of spores is termed 'superdormant (SD) spores.' Depending on the source of the germination stimulus, SD spores are categorized as nutrient-SD spores, Ca2+-dipicolinic acid SD spores, dodecylamine-SD spores, and high pressure SD spores. In recent decades, research has been done to isolate these different groups of SD spores and unravel the cause of their germination deficiency as well as their germination capacities. This review summarizes the challenges caused by SD spores, their isolation and characterization, the underlying mechanisms of their germination deficiency, and the future research directions needed to tackle this topic in further depth.
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Affiliation(s)
| | - Alexander Mathys
- Sustainable Food Processing Laboratory, Institute of Food, Nutrition and Health, Department of Health Science and Technology, ETH Zurich, Zurich, Switzerland
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Granger JH, Porter MD. The Case for Human Serum as a Highly Preferable Sample Matrix for Detection of Anthrax Toxins. ACS Sens 2018; 3:2303-2310. [PMID: 30350950 DOI: 10.1021/acssensors.8b00566] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
This paper describes preliminary results on the surprising impact of human serum as a sample matrix on the detectability of protective antigen (PA) and lethal factor (LF), two antigenic protein markers of Bacillus anthracis, in a heterogeneous immunometric assay. Two sample matrices were examined: human serum and physiological buffer. Human serum is used as a specimen in the diagnostic testing of potentially infected individuals. Physiological buffers are often applied to the recovery of biomarkers dispersed in suspicious white powders and other suspect specimens and as a serum diluent to combat contributions to the measured test response from nonspecific adsorption. The results of these experiments using a sandwich immunoassay read out by surface-enhanced Raman scattering yielded estimates for the limit of detection (LOD) for both markers when using spiked human serum that were remarkably lower than those of spiked physiological buffer (∼70,000× for PA and ∼25,000× for LF). The difference in LODs is attributed to a degradation in the effectiveness of the capture and/or labeling steps in the immunoassay due to the known propensity for both proteins to denature in buffer. These findings indicate that the use of physiological buffer for serum dilution or recovery from a powdered matrix is counter to the low-level detection of these two antigenic proteins. The potential implications of these results with respect to the ability to detect markers of other pathogenic agents are briefly discussed.
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Sedlackova V, Dziedzinska R, Babak V, Kralik P. The detection and quantification of Bacillus thuringiensis
spores from soil and swabs using quantitative PCR as a model system for routine diagnostics of Bacillus anthracis. J Appl Microbiol 2017; 123:116-123. [DOI: 10.1111/jam.13445] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Revised: 02/14/2017] [Accepted: 03/03/2017] [Indexed: 11/27/2022]
Affiliation(s)
| | | | - V. Babak
- Veterinary Research Institute; Brno Czech Republic
| | - P. Kralik
- Veterinary Research Institute; Brno Czech Republic
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7
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Silvestri EE, Yund C, Taft S, Bowling CY, Chappie D, Garrahan K, Brady-Roberts E, Stone H, Nichols TL. Considerations for estimating microbial environmental data concentrations collected from a field setting. JOURNAL OF EXPOSURE SCIENCE & ENVIRONMENTAL EPIDEMIOLOGY 2017; 27:141-151. [PMID: 26883476 PMCID: PMC5318663 DOI: 10.1038/jes.2016.3] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 12/07/2015] [Indexed: 06/05/2023]
Abstract
In the event of an indoor release of an environmentally persistent microbial pathogen such as Bacillus anthracis, the potential for human exposure will be considered when remedial decisions are made. Microbial site characterization and clearance sampling data collected in the field might be used to estimate exposure. However, there are many challenges associated with estimating environmental concentrations of B. anthracis or other spore-forming organisms after such an event before being able to estimate exposure. These challenges include: (1) collecting environmental field samples that are adequate for the intended purpose, (2) conducting laboratory analyses and selecting the reporting format needed for the laboratory data, and (3) analyzing and interpreting the data using appropriate statistical techniques. This paper summarizes some key challenges faced in collecting, analyzing, and interpreting microbial field data from a contaminated site. Although the paper was written with considerations for B. anthracis contamination, it may also be applicable to other bacterial agents. It explores the implications and limitations of using field data for determining environmental concentrations both before and after decontamination. Several findings were of interest. First, to date, the only validated surface/sampling device combinations are swabs and sponge-sticks on stainless steel surfaces, thus limiting availability of quantitative analytical results which could be used for statistical analysis. Second, agreement needs to be reached with the analytical laboratory on the definition of the countable range and on reporting of data below the limit of quantitation. Finally, the distribution of the microbial field data and statistical methods needed for a particular data set could vary depending on these data that were collected, and guidance is needed on appropriate statistical software for handling microbial data. Further, research is needed to develop better methods to estimate human exposure from pathogens using environmental data collected from a field setting.
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Affiliation(s)
- Erin E Silvestri
- United States Environmental Protection Agency, National Homeland Security Research Center, Threat Consequence Assessment Division, Cincinnati, Ohio, USA
| | - Cynthia Yund
- United States Environmental Protection Agency, National Homeland Security Research Center, Threat Consequence Assessment Division, Cincinnati, Ohio, USA
| | - Sarah Taft
- United States Environmental Protection Agency, National Homeland Security Research Center, Threat Consequence Assessment Division, Cincinnati, Ohio, USA
| | - Charlena Yoder Bowling
- United States Environmental Protection Agency, National Homeland Security Research Center, Threat Consequence Assessment Division, Cincinnati, Ohio, USA
| | | | | | - Eletha Brady-Roberts
- United States Environmental Protection Agency, National Homeland Security Research Center, Threat Consequence Assessment Division, Cincinnati, Ohio, USA
| | - Harry Stone
- Battelle Memorial Institute, Columbus, Ohio, USA
| | - Tonya L Nichols
- United States Environmental Protection Agency, National Homeland Security Research Center, Threat Consequence Assessment Division, Washington DC, USA
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8
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Silvestri EE, Feldhake D, Griffin D, Lisle J, Nichols TL, Shah SR, Pemberton A, Schaefer FW. Optimization of a sample processing protocol for recovery of Bacillus anthracis spores from soil. J Microbiol Methods 2016; 130:6-13. [PMID: 27546718 DOI: 10.1016/j.mimet.2016.08.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 08/17/2016] [Accepted: 08/17/2016] [Indexed: 10/21/2022]
Abstract
Following a release of Bacillus anthracis spores into the environment, there is a potential for lasting environmental contamination in soils. There is a need for detection protocols for B. anthracis in environmental matrices. However, identification of B. anthracis within a soil is a difficult task. Processing soil samples helps to remove debris, chemical components, and biological impurities that can interfere with microbiological detection. This study aimed to optimize a previously used indirect processing protocol, which included a series of washing and centrifugation steps. Optimization of the protocol included: identifying an ideal extraction diluent, variation in the number of wash steps, variation in the initial centrifugation speed, sonication and shaking mechanisms. The optimized protocol was demonstrated at two laboratories in order to evaluate the recovery of spores from loamy and sandy soils. The new protocol demonstrated an improved limit of detection for loamy and sandy soils over the non-optimized protocol with an approximate matrix limit of detection at 14spores/g of soil. There were no significant differences overall between the two laboratories for either soil type, suggesting that the processing protocol will be robust enough to use at multiple laboratories while achieving comparable recoveries.
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Affiliation(s)
- Erin E Silvestri
- U.S. Environmental Protection Agency, National Homeland Security Research Center, 26 W. Martin Luther King Drive, MS NG16, Cincinnati, OH 45268, United States.
| | - David Feldhake
- Pegasus Technical Services, Inc., 46 East Hollister St., Cincinnati, OH 45219, United States.
| | - Dale Griffin
- U. S. Geological Survey, Coastal and Marine Science Center, 600 4th Street South, St. Petersburg, FL 33701, United States.
| | - John Lisle
- U. S. Geological Survey, Coastal and Marine Science Center, 600 4th Street South, St. Petersburg, FL 33701, United States.
| | - Tonya L Nichols
- U.S. Environmental Protection Agency, National Homeland Security Research Center, 1200 Pennsylvania Avenue, N.W., MS 8801R, Washington D.C. 20460, United States.
| | - Sanjiv R Shah
- U.S. Environmental Protection Agency, National Homeland Security Research Center, 1200 Pennsylvania Avenue, N.W., MS 8801R, Washington D.C. 20460, United States.
| | - Adin Pemberton
- Pegasus Technical Services, Inc., 46 East Hollister St., Cincinnati, OH 45219, United States.
| | - Frank W Schaefer
- U.S. Environmental Protection Agency, National Homeland Security Research Center, 26 W. Martin Luther King Drive, MS NG16, Cincinnati, OH 45268, United States.
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9
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Turner WC, Kausrud KL, Beyer W, Easterday WR, Barandongo ZR, Blaschke E, Cloete CC, Lazak J, Van Ert MN, Ganz HH, Turnbull PCB, Stenseth NC, Getz WM. Lethal exposure: An integrated approach to pathogen transmission via environmental reservoirs. Sci Rep 2016; 6:27311. [PMID: 27265371 PMCID: PMC4893621 DOI: 10.1038/srep27311] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Accepted: 05/11/2016] [Indexed: 11/09/2022] Open
Abstract
To mitigate the effects of zoonotic diseases on human and animal populations, it is critical to understand what factors alter transmission dynamics. Here we assess the risk of exposure to lethal concentrations of the anthrax bacterium, Bacillus anthracis, for grazing animals in a natural system over time through different transmission mechanisms. We follow pathogen concentrations at anthrax carcass sites and waterholes for five years and estimate infection risk as a function of grass, soil or water intake, age of carcass sites, and the exposure required for a lethal infection. Grazing, not drinking, seems the dominant transmission route, and transmission is more probable from grazing at carcass sites 1-2 years of age. Unlike most studies of virulent pathogens that are conducted under controlled conditions for extrapolation to real situations, we evaluate exposure risk under field conditions to estimate the probability of a lethal dose, showing that not all reservoirs with detectable pathogens are significant transmission pathways.
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Affiliation(s)
- Wendy C Turner
- Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, P.O. Box 1066 Blindern, 0361 Oslo, Norway.,Department of Biological Sciences, State University of New York, Albany, New York 12222, USA.,Department of Environmental Science, Policy and Management, University of California, Berkeley, 137 Mulford Hall, Berkeley, CA 94720-3112, USA
| | - Kyrre L Kausrud
- Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, P.O. Box 1066 Blindern, 0361 Oslo, Norway
| | - Wolfgang Beyer
- Institute of Animal Sciences, Department of Environmental and Animal Hygiene, University of Hohenheim, Hohenheim, Germany
| | - W Ryan Easterday
- Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, P.O. Box 1066 Blindern, 0361 Oslo, Norway
| | - Zoë R Barandongo
- Department of Biological Sciences, Faculty of Science, University of Namibia, Windhoek, Namibia
| | - Elisabeth Blaschke
- Institute of Animal Sciences, Department of Environmental and Animal Hygiene, University of Hohenheim, Hohenheim, Germany
| | - Claudine C Cloete
- Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, P.O. Box 1066 Blindern, 0361 Oslo, Norway.,Department of Biological Sciences, Faculty of Science, University of Namibia, Windhoek, Namibia.,Etosha Ecological Institute, Ministry of Environment and Tourism, Etosha National Park, PO Box 6, Okaukuejo, Namibia
| | - Judith Lazak
- Institute of Animal Sciences, Department of Environmental and Animal Hygiene, University of Hohenheim, Hohenheim, Germany.,Institute of International Animal Health, Free University of Berlin, Königsweg 67, 14163 Berlin, Germany
| | - Matthew N Van Ert
- Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA
| | - Holly H Ganz
- Department of Environmental Science, Policy and Management, University of California, Berkeley, 137 Mulford Hall, Berkeley, CA 94720-3112, USA.,Genome Center and Department of Evolution and Ecology, University of California, Davis, CA, USA
| | | | - Nils Chr Stenseth
- Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, P.O. Box 1066 Blindern, 0361 Oslo, Norway
| | - Wayne M Getz
- Department of Environmental Science, Policy and Management, University of California, Berkeley, 137 Mulford Hall, Berkeley, CA 94720-3112, USA.,School of Mathematical Sciences, University of KwaZulu-Natal, Private Bag X54001, Durban 4000, South Africa
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10
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Rapid Detection of Viable Bacillus anthracis Spores in Environmental Samples by Using Engineered Reporter Phages. Appl Environ Microbiol 2016; 82:2380-2387. [PMID: 26873316 DOI: 10.1128/aem.03772-15] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Accepted: 02/04/2016] [Indexed: 12/26/2022] Open
Abstract
Bacillus anthracis, the causative agent of anthrax, was utilized as a bioterrorism agent in 2001 when spores were distributed via the U.S. postal system. In responding to this event, the Federal Bureau of Investigation used traditional bacterial culture viability assays to ascertain the extent of contamination of the postal facilities within 24 to 48 h of environmental sample acquisition. Here, we describe a low-complexity, second-generation reporter phage assay for the rapid detection of viableB. anthracis spores in environmental samples. The assay uses an engineered B. anthracis reporter phage (Wβ::luxAB-2) which transduces bioluminescence to infected cells. To facilitate low-level environmental detection and maximize the signal response, expression of luxABin an earlier version of the reporter phage (Wβ::luxAB-1) was optimized. These alterations prolonged signal kinetics, increased light output, and improved assay sensitivity. Using Wβ::luxAB-2, detection of B. anthracis spores was 1 CFU in 8 h from pure cultures and as low as 10 CFU/g in sterile soil but increased to 10(5)CFU/g in unprocessed soil due to an unstable signal and the presence of competing bacteria. Inclusion of semiselective medium, mediated by a phage-expressed antibiotic resistance gene, maintained signal stability and enabled the detection of 10(4)CFU/g in 6 h. The assay does not require spore extraction and relies on the phage infecting germinating cells directly in the soil sample. This reporter phage displays promise for the rapid detection of low levels of spores on clean surfaces and also in grossly contaminated environmental samples from complex matrices such as soils.
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