Recovery Efficiencies of Anthrax Spores and Ricin from Nonporous or Nonabsorbent and Porous or Absorbent Surfaces by a Variety of Sampling Methods*

In Situ Visualization of Particle Motions during Wipe Sampling of Explosives and Other Trace Particulate Materials

Surface texture tailoring has the potential to increase the effectiveness of dry particle collection wipes, as a wipe's topographical features control the intimate surface contact made with particles on the substrate (critical for van der Waals-governed adhesion). However, texture-tailoring approaches have not yet been widely explored, in part because of a lack of understanding of the specific wipe topographies and wipe/particle interactions that maximize particle collection. Here we describe an in situ optical microscopy technique that enables direct observation of micrometer-scale particle-wipe interactions occurring at the wipe-substrate interface during contact sampling. The technique is demonstrated for nonwoven meta-aramid (Nomex) collection wipes with particles ranging from 1 to 90 μm in diameter and substrates of different topographies (glass and nylon coil zipper). Experiments with hemispherically coated Janus particles allow rolling motions to be distinguished from sliding motions, providing detailed information about how particles move prior to capture or release by the wipe. Particle-fiber and particle-particle interactions are seen to play important roles in particle capture, suggesting that conventional sphere-on-plane models are inadequate to describe adhesion behavior in these systems. Micrographs show how loose, flexible fibers in roughened textile wipes interrogate the valleys of uneven substrate topographies, allowing capture of particles that might otherwise be trapped within the substrate's grooves and depressions. The materials used in this work are specifically relevant to explosives detection, but the in situ visualization technique is transferable for the study of any application involving dry particle collection, such as toxic substance sampling and dust removal.

Alternative fast analysis method for cellulose sponge surface sampling wipes with low concentrations of Bacillus Spores

Environmental sampling is a critical component of the post decontamination verification process following a bioterrorism event. The current work was performed to produce a less labor-intensive method for processing cellulose sponge-wipes used for sampling areas potentially contaminated with low concentrations (i.e., post-decontamination) of Bacillus anthracis spores. An alternative fast-analysis processing method was compared to the processing protocol validated by the Centers for Disease Control and Prevention (CDC) for the Laboratory Response Network (LRN). Glazed tile coupons (1102 cm²) were inoculated with 50, 500, or 5000 spores of Bacillus thuringiensis subsp. kurstaki (Btk), then sampled with cellulose sponges. Sampling was limited to a 25- by 25-cm area and performed in the same manner as the CDC sampling method. Samples were then processed using either the alternative "Fast Analysis" method or the "CDC method". Three different analysts repeated the tests at each concentration utilizing each method. Mean recoveries, labor time, and potentially hazardous waste produced were compared for the two methods. The mean percent recoveries and standard errors for the samples processed using the "CDC method" were 39.9 ± 6.7, 43 ± 7.6, and 36.8 ± 10.1 for the 5000, 500, and 50 spore loading levels, respectively; compared to 54.2 ± 12.9, 64.2 ± 21.7, and 45.2 ± 8.6 for the "Fast Analysis" method. At each titer tested the "Fast Analysis" method resulted in a statistically significant higher percent recovery. Furthermore, analysts processed samples utilizing the "Fast Analysis" method in less than half the time and generated half as much potentially hazardous waste compared to the "CDC method".

Comparison of false-negative rates and limits of detection following macrofoam-swab sampling of Bacillus anthracis surrogates via Rapid Viability PCR and plate culture

AIMS

We evaluated the effects of Bacillus anthracis surrogates, low surface concentrations, surface materials and assay methods on false-negative rate (FNR) and limit of detection (LOD₉₅ ) for recovering Bacillus spores using a macrofoam-swab sampling procedure.

METHODS AND RESULTS

Bacillus anthracis Sterne or Bacillus atrophaeus Nakamura spores were deposited over a range of low target concentrations (2-500 per coupon) onto glass, stainless steel, vinyl tile and plastic. Samples were assayed using a modified Rapid Viability-PCR (mRV-PCR) method and the traditional plate culture method to obtain FNR and LOD₉₅ results.

CONCLUSIONS

Mean FNRs tended to be lower for mRV-PCR compared to culturing, and increased as spore concentration decreased for all surface materials. Surface material, but not B. anthracis surrogate, influenced FNRs with the mRV-PCR method. The mRV-PCR LOD₉₅ was lowest for glass and highest for vinyl tile. LOD₉₅ values overall were lower for mRV-PCR than for the culture method.

SIGNIFICANCE AND IMPACT OF STUDY

This study adds to the limited data on FNR and LOD₉₅ for mRV-PCR and culturing methods with low concentrations of B. anthracis sampled from various surface materials by the CDC macrofoam-swab method. These are key inputs for planning characterization and clearance studies for low contamination levels of B. anthracis.

Effect of Sterilants on Amplification and Detection of Target DNA from Bacillus cereus Spores

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.

Considerations for estimating microbial environmental data concentrations collected from a field setting

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.

Persistence of influenza on surfaces

BACKGROUND

Close contact transmission (either direct or large droplet/droplet nuclei) is considered the main driver of influenza outbreaks but there is limited information regarding the role of fomites in transmission.

AIM

To investigate the surface stability of influenza strains and thereby the role of fomites in transmission.

METHODS

The viability and quantitative reverse transcription-polymerase chain reaction (qt-RT-PCR) signal of five influenza strains (A/PR/8/34/H1N1, A/Cal/7/09/H1N1, A/Cal/4/09/H1N1, A/Sol/54/06/H1N1, and A/Bris/59/07/H1N1) seeded on to three surfaces (cotton, microfibre, and stainless steel) were assessed over time. Coupons of material were seeded with 10μL of a 10⁶-10⁸pfu/mL suspension of cell culture-derived virus stock supplemented with 0.3% bovine serum albumin. Coupons were assayed by plaque assay and qt-RT-PCR at 1, 24h, and weekly for seven weeks using a vortex-mixing elution method.

FINDINGS

Viable virus was detected from coupons for up to two weeks (stainless steel) and one week (cotton and microfibre), whereas detection of viruses by PCR was made for the entire seven-week study period. No strain differences were found. Ninety-nine percent reduction values (as a function of the seeding stock) were determined to be 17.7h for cotton (R²=0.86), 34.3h for microfibre (R²=0.80), and 174.9h for stainless steel (R²=0.98).

CONCLUSION

Viable influenza was recovered from surfaces for up to two weeks. By contrast, influenza could be detected by PCR for more than seven weeks. These results have important implications for determining infection control protocols, cleaning regimes and sampling methods in healthcare settings.

Extraction of Aerosol-Deposited Yersinia pestis from Indoor Surfaces To Determine Bacterial Environmental Decay

Public health and decontamination decisions following an event that causes indoor contamination with a biological agent require knowledge of the environmental persistence of the agent. The goals of this study were to develop methods for experimentally depositing bacteria onto indoor surfaces via aerosol, evaluate methods for sampling and enumerating the agent on surfaces, and use these methods to determine bacterial surface decay. A specialized aerosol deposition chamber was constructed, and methods were established for reproducible and uniform aerosol deposition of bacteria onto four coupon types. The deposition chamber facilitated the control of relative humidity (RH; 10 to 70%) following particle deposition to mimic the conditions of indoor environments, as RH is not controlled by standard heating, ventilation, and air conditioning (HVAC) systems. Extraction and culture-based enumeration methods to quantify the viable bacteria on coupons were shown to be highly sensitive and reproducible. To demonstrate the usefulness of the system for decay studies,Yersinia pestis persistence as a function of surface type at 21 °C and 40% RH was determined to be >40%/min for all surfaces. Based upon these results, at typical indoor temperature and RH, a 6-log reduction in titer would expected to be achieved within 1 h as the result of environmental decay on surfaces without active decontamination. The developed approach will facilitate future persistence and decontamination studies with a broad range of biological agents and surfaces, providing agent decay data to inform both assessments of risk to personnel entering a contaminated site and decontamination decisions following biological contamination of an indoor environment.

IMPORTANCE

Public health and decontamination decisions following contamination of an indoor environment with a biological agent require knowledge of the environmental persistence of the agent. Previous studies on Y. pestis persistence have utilized large liquid droplet deposition to provide persistence data. As a result, methods were developed to deposit aerosols containing bacteria onto indoor surfaces, reproducibly enumerate bacteria harvested from coupons, and determine surface decay utilizing Y. pestis The results of this study provide foundational methods required to evaluate surface decay of bacteria and potentially other biological agents, such as viruses, in aerosol particles as a function of surface type and environment. Integrating the data from both aerosol and liquid deposition surface decay studies will provide medical and public health personnel with a more complete understanding of agent persistence on surfaces in contaminated areas for assessment of health risks and to inform decontamination decisions.

False-negative rate, limit of detection and recovery efficiency performance of a validated macrofoam-swab sampling method for low surface concentrations of Bacillus anthracis Sterne and Bacillus atrophaeus spores

AIMS

We sought to evaluate the effects of Bacillus species, low surface concentrations, and surface material on recovery efficiency (RE), false-negative rate (FNR) and limit of detection for recovering Bacillus spores using a validated macrofoam-swab sampling procedure.

METHODS AND RESULTS

The performance of a macrofoam-swab sampling method was evaluated using Bacillus anthracis Sterne (BAS) and Bacillus atrophaeus Nakamura (BG) spores applied at nine low target surface concentrations (2 to 500 CFU per plate or coupon) to positive-control plates and test coupons (25·8064 cm(2) ) of four surface materials (glass, stainless steel, vinyl tile and plastic). The Bacillus species and surface material had statistically significant effects on RE, but surface concentration did not. Mean REs were the lowest for vinyl tile (50·8% with BAS and 40·2% with BG) and the highest for glass (92·8% with BAS and 71·4% with BG). FNR values (which ranged from 0 to 0·833 for BAS and from 0 to 0·806 for BG) increased as surface concentration decreased in the range tested. Surface material also had a statistically significant effect on FNR, with FNR the lowest for glass and highest for vinyl tile. Finally, FNR tended to be higher for BG than for BAS at lower surface concentrations, especially for glass.

CONCLUSIONS

Concentration and surface material had significant effects on FNR, with Bacillus species having a small effect. Species and surface material had significant effects on RE, with surface concentration having a nonsignificant effect.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results provide valuable information on the performance of the macrofoam-swab method for low surface concentrations of Bacillus spores, which can be adapted to assess the likelihood that there is no contamination when all macrofoam-swab samples fail to detect B. anthracis.

Updating a B. anthracis Risk Model with Field Data from a Bioterrorism Incident

In this study, a Bayesian framework was applied to update a model of pathogen fate and transport in the indoor environment. Distributions for model parameters (e.g., release quantity of B. anthracis spores, risk of illness, spore setting velocity, resuspension rate, sample recovery efficiency, etc.) were updated by comparing model predictions with measurements of B. anthracis spores made after one of the 2001 anthrax letter attacks. The updating process, which was implemented by using Markov chain Monte Carlo (MCMC) methods, significantly reduced the uncertainties of inputs with uniformed prior estimates: total quantity of spores released, the amount of spores exiting the room, and risk to occupants. In contrast, uncertainties were not greatly reduced for inputs for which informed prior data were available: deposition rates, resuspension rates, and sample recovery efficiencies. This suggests that prior estimates of these quantities that were obtained from a review of the technical literature are consistent with the observed behavior of spores in an actual attack. Posterior estimates of mortality risk for people in the room, when the spores were released, are on the order of 0.01 to 0.1, which supports the decision to administer prophylactic antibiotics. Multivariate sensitivity analyses were conducted to assess how effective different measurements were at reducing uncertainty in the estimated risk for the prior scenario. This analysis revealed that if the size distribution of the released particulates is known, then environmental sampling can be limited to accurately characterizing floor concentrations; otherwise, samples from multiple locations, as well as particulate and building air circulation parameters, need to be measured.

Development of an ELISA for evaluation of swab recovery efficiencies of bovine serum albumin

After a potential biological incident the sampling strategy and sample analysis are crucial for the outcome of the investigation and identification. In this study, we have developed a simple sandwich ELISA based on commercial components to quantify BSA (used as a surrogate for ricin) with a detection range of 1.32–80 ng/mL. We used the ELISA to evaluate different protein swabbing procedures (swabbing techniques and after-swabbing treatments) for two swab types: a cotton gauze swab and a flocked nylon swab. The optimal swabbing procedure for each swab type was used to obtain recovery efficiencies from different surface materials. The surface recoveries using the optimal swabbing procedure ranged from 0–60% and were significantly higher from nonporous surfaces compared to porous surfaces. In conclusion, this study presents a swabbing procedure evaluation and a simple BSA ELISA based on commercial components, which are easy to perform in a laboratory with basic facilities. The data indicate that different swabbing procedures were optimal for each of the tested swab types, and the particular swab preference depends on the surface material to be swabbed.

Comparative evaluation of vacuum-based surface sampling methods for collection of Bacillus spores

In this study, four commonly-used sampling devices (vacuum socks, 37 mm 0.8 μm mixed cellulose ester (MCE) filter cassettes, 37 mm 0.3 μm polytetrafluoroethylene (PTFE) filter cassettes, and 3M™ forensic filters) were comparatively evaluated for their ability to recover surface-associated spores. Aerosolized spores (~10(5)CFUcm(-2)) of a Bacillus anthracis surrogate were allowed to settle onto three material types (concrete, carpet, and upholstery). Ten replicate samples were collected using each vacuum method, from each material type. Stainless steel surfaces, inoculated simultaneously with test materials, were sampled with pre-moistened wipes. Wipe recoveries were utilized to normalize vacuum-based recoveries across trials. Recovery (CFUcm(-2)) and relative recovery (vacuum recovery/wipe recovery) were determined for each method and material type. Recoveries and relative recoveries ranged from 3.8 × 10(3) to 7.4 × 10(4)CFUcm(-2) and 0.035 to 1.242, respectively. ANOVA results indicated that the 37 mm MCE method exhibited higher relative recoveries than the other methods when used for sampling concrete or upholstery. While the vacuum sock resulted in the highest relative recoveries on carpet, no statistically significant difference was detected. The results of this study may be used to guide selection of sampling approaches following biological contamination incidents.

Detecting laboratory DNA contamination using polyester-rayon wipes: a method validation study

Due to the high sensitivity of many PCR assays, extraneous target DNA in a laboratory setting can lead to false positive results. To assess the presence of extraneous DNA, many laboratories use gauze wipes to sample laboratory surfaces. The accuracy, precision, limits of detection, linearity, and robustness of a wipe test method and each associated wipe processing step were evaluated using E. coli genomic DNA. The method demonstrated a limit of detection of 108 copies of DNA, which equates to detectable surface concentration of 4.5×10(5) copies of DNA per area sampled. Recovery efficiency or accuracy is 22±10% resulting from a >58% loss of DNA occurring at the wipe wash step. The method is robust, performing consistently despite deliberate modifications of the protocol.

Storage Effects on Sample Integrity of Environmental Surface Sampling Specimens with Bacillus anthracis Spores

The effect of packaging, shipping temperatures and storage times on recovery of Bacillus anthracis. Sterne spores from swabs was investigated. Macrofoam swabs were pre-moistened, inoculated with Bacillus anthracis spores, and packaged in primary containment or secondary containment before storage at -15°C, 5°C, 21°C, or 35°C for 0-7 days. Swabs were processed according to validated Centers for Disease Control/Laboratory Response Network culture protocols, and the percent recovery relative to a reference sample (T₀) was determined for each variable. No differences were observed in recovery between swabs held at -15° and 5°C, (p ≥ 0.23). These two temperatures provided significantly better recovery than swabs held at 21°C or 35°C (all 7 days pooled, p ≤ 0.04). The percent recovery at 5°C was not significantly different if processed on days 1, 2 or 4, but was significantly lower on day 7 (day 2 vs. 7, 5°C, 10², p=0.03). Secondary containment provided significantly better percent recovery than primary containment, regardless of storage time (5°C data, p ≤ 0.008). The integrity of environmental swab samples containing Bacillus anthracis spores shipped in secondary containment was maintained when stored at -15°C or 5°C and processed within 4 days to yield the optimum percent recovery of spores.

Laboratory studies on surface sampling of Bacillus anthracis contamination: summary, gaps and recommendations

This article summarizes previous laboratory studies to characterize the performance of methods for collecting, storing/transporting, processing and analysing samples from surfaces contaminated by Bacillus anthracis or related surrogates. The focus is on plate culture and count estimates of surface contamination for swab, wipe and vacuum samples of porous and nonporous surfaces. Summaries of the previous studies and their results were assessed to identify gaps in information needed as inputs to calculate key parameters critical to risk management in biothreat incidents. One key parameter is the number of samples needed to make characterization or clearance decisions with specified statistical confidence. Other key parameters include the ability to calculate, following contamination incidents, the (i) estimates of B. anthracis contamination, as well as the bias and uncertainties in the estimates and (ii) confidence in characterization and clearance decisions for contaminated or decontaminated buildings. Gaps in knowledge and understanding identified during the summary of the studies are discussed. Additional work is needed to quantify (i) the false-negative rates of surface-sampling methods with lower concentrations on various surfaces and (ii) the effects on performance characteristics of: aerosol vs liquid deposition of spores, using surrogates instead of B. anthracis, real-world vs laboratory conditions and storage and transportation conditions. Recommendations are given for future evaluations of data from existing studies and possible new studies.

Characterizing bioaerosol risk from environmental sampling

In the aftermath of a release of microbiological agents, environmental sampling must be conducted to characterize the release sufficiently so that mathematical models can then be used to predict the subsequent dispersion and human health risks. Because both the dose-response and environmental transport of aerosolized microbiological agents are functions of the effective aerodynamic diameter of the particles, environmental assessments should consider not only the total amount of agents but also the size distributions of the aerosolized particles. However, typical surface sampling cannot readily distinguish among different size particles. This study evaluates different approaches to estimating risk from measurements of microorganisms deposited on surfaces after an aerosol release. For various combinations of sampling surfaces, size fractions, HVAC operating conditions, size distributions of release spores, uncertainties in surface measurements, and the accuracy of model predictions are tested in order to assess how much detail can realistically be identified from surface sampling results. The recommended modeling and sampling scheme is one choosing 3, 5, and 10 μm diameter particles as identification targets and taking samples from untracked floor, wall, and the HVAC filter. This scheme provides reasonably accurate, but somewhat conservative, estimates of risk across a range of different scenarios. Performance of the recommended sampling scheme is tested by using data from a large-scale field test as a case study. Sample sizes of 10-25 in each homogeneously mixed environmental compartment are sufficient to develop order of magnitude estimates of risk. Larger sample sizes have little benefit unless uncertainties in sample recoveries can be reduced.

Impact of processing method on recovery of bacteria from wipes used in biological surface sampling

Environmental sampling for microbiological contaminants is a key component of hygiene monitoring and risk characterization practices utilized across diverse fields of application. However, confidence in surface sampling results, both in the field and in controlled laboratory studies, has been undermined by large variation in sampling performance results. Sources of variation include controlled parameters, such as sampling materials and processing methods, which often differ among studies, as well as random and systematic errors; however, the relative contributions of these factors remain unclear. The objective of this study was to determine the relative impacts of sample processing methods, including extraction solution and physical dissociation method (vortexing and sonication), on recovery of Gram-positive (Bacillus cereus) and Gram-negative (Burkholderia thailandensis and Escherichia coli) bacteria from directly inoculated wipes. This work showed that target organism had the largest impact on extraction efficiency and recovery precision, as measured by traditional colony counts. The physical dissociation method (PDM) had negligible impact, while the effect of the extraction solution was organism dependent. Overall, however, extraction of organisms from wipes using phosphate-buffered saline with 0.04% Tween 80 (PBST) resulted in the highest mean recovery across all three organisms. The results from this study contribute to a better understanding of the factors that influence sampling performance, which is critical to the development of efficient and reliable sampling methodologies relevant to public health and biodefense.

Comparison of quantitative PCR and culture-based methods for evaluating dispersal of Bacillus thuringiensis endospores at a bioterrorism hoax crime scene

Since the anthrax mail attacks of 2001, law enforcement agencies have processed thousands of suspicious mail incidents globally, many of which are hoax bioterrorism threats. Bio-insecticide preparations containing Bacillus thuringiensis (Bt) spores have been involved in several such threats in Australia, leading to the requirement for rapid and sensitive detection techniques for this organism, a close relative of Bacillus anthracis. Here we describe the development of a quantitative PCR (qPCR) method for the detection of Bt crystal toxin gene cry1, and evaluation of the method's effectiveness during a hoax bioterrorism event in 2009. When combined with moist wipe sampling, the cry1 qPCR was a rapid, reliable, and sensitive diagnostic tool for detecting and quantifying Bt contamination, and mapping endospore dispersal within a mail sorting facility. Results from the cry1 qPCR were validated by viable counts of the same samples on Bacillus-selective agar (PEMBA), which revealed a similar pattern of contamination. Extensive and persistent contamination of the facility was detected, both within the affected mailroom, and extending into office areas up to 30m distant from the source event, emphasising the need for improved containment procedures for suspicious mail items, both during and post-event. The cry1 qPCR enables detection of both viable and non-viable Bt spores and cells, which is important for historical crime scenes or scenes subjected to decontamination. This work provides a new rapid method to add to the forensics toolbox for crime scenes suspected to be contaminated with biological agents.

False-negative rate and recovery efficiency performance of a validated sponge wipe sampling method

Recovery of spores from environmental surfaces varies due to sampling and analysis methods, spore size and characteristics, surface materials, and environmental conditions. Tests were performed to evaluate a new, validated sponge wipe method using Bacillus atrophaeus spores. Testing evaluated the effects of spore concentration and surface material on recovery efficiency (RE), false-negative rate (FNR), limit of detection (LOD), and their uncertainties. Ceramic tile and stainless steel had the highest mean RE values (48.9 and 48.1%, respectively). Faux leather, vinyl tile, and painted wood had mean RE values of 30.3, 25.6, and 25.5, respectively, while plastic had the lowest mean RE (9.8%). Results show roughly linear dependences of RE and FNR on surface roughness, with smoother surfaces resulting in higher mean REs and lower FNRs. REs were not influenced by the low spore concentrations tested (3.10 × 10(-3) to 1.86 CFU/cm(2)). Stainless steel had the lowest mean FNR (0.123), and plastic had the highest mean FNR (0.479). The LOD(90) (≥1 CFU detected 90% of the time) varied with surface material, from 0.015 CFU/cm(2) on stainless steel up to 0.039 on plastic. It may be possible to improve sampling results by considering surface roughness in selecting sampling locations and interpreting spore recovery data. Further, FNR values (calculated as a function of concentration and surface material) can be used presampling to calculate the numbers of samples for statistical sampling plans with desired performance and postsampling to calculate the confidence in characterization and clearance decisions.

Suitability of Commercial Transport Media for Biological Pathogens under Nonideal Conditions

There is extensive data to support the use of commercial transport media as a stabilizer for known clinical samples; however, there is little information to support their use outside of controlled conditions specified by the manufacturer. Furthermore, there is no data to determine the suitability of said media for biological pathogens, specifically those of interest to the US military. This study evaluates commercial off-the-shelf (COTS) transport media based on sample recovery, viability, and quality of nucleic acids and peptides for nonpathogenic strains of Bacillus anthracis, Yersinia pestis, and Venezuelan equine encephalitis virus, in addition to ricin toxin. Samples were stored in COTS, PBST, or no media at various temperatures over an extended test period. The results demonstrate that COTS media, although sufficient for the preservation of nucleic acid and proteinaceous material, are not capable of maintaining an accurate representation of biothreat agents at the time of collection.

National validation study of a cellulose sponge wipe-processing method for use after sampling Bacillus anthracis spores from surfaces

This work was initiated to address the gaps identified by Congress regarding validated biothreat environmental sampling and processing methods. Nine Laboratory Response Network-affiliated laboratories participated in a validation study of a cellulose sponge wipe-processing protocol for the recovery, detection, and quantification of viable Bacillus anthracis Sterne spores from steel surfaces. Steel coupons (645.16 cm(2)) were inoculated with 1 to 4 log(10) spores and then sampled with cellulose sponges (Sponge-Stick; 3M, St. Paul, MN). Surrogate dust and background organisms were added to the sponges to mimic environmental conditions. Labs processed the sponges according to the provided protocol. Sensitivity, specificity, and mean percent recovery (%R), between-lab variability, within-lab variability, and total percent coefficient of variation were calculated. The mean %R (standard error) of spores from the surface was 32.4 (4.4), 24.4 (2.8), and 30.1 (2.3) for the 1-, 2-, and 4-log(10) inoculum levels, respectively. Sensitivities for colony counts were 84.1%, 100%, and 100% for the 1-, 2-, and 4-log(10) inocula, respectively. These data help to characterize the variability of the processing method and thereby enhance confidence in the interpretation of the results of environmental sampling conducted during a B. anthracis contamination investigation.

Bioterrorism: the effects of biological decontamination on the recovery of electronic evidence

The investigation of a bioterrorism event will ultimately lead to the collection of vital data from electronic devices such as computers and mobile phones. This project sought to determine the use of gamma irradiation and formaldehyde gas as effective biological decontaminants, and the effect of these methods on the recovery of electronic evidence. Electronic items were contaminated with viable spores and then exposed to both decontaminants. Log values for each matrix were calculated with flash drives recording the highest value of 566 Gy for gamma irradiation and a maximum of 50 min exposure to formaldehyde saw the effective destruction of spores. The results indicate that recovery of data varied based on the decontaminant selected, formaldehyde gas giving the most promising results, with electronic data recovered after the required exposure time. Gamma irradiation proved damaging to electronic circuitry at levels required to render the items safe. The implications to computer intelligence and forensics will be discussed based on the outcomes of these findings.

Parameters affecting spore recovery from wipes used in biological surface sampling

The need for the precise and reliable collection of potential biothreat contaminants has motivated research in developing a better understanding of the variability in biological surface sampling methods. In this context, the objective of this work was to determine parameters affecting the efficiency of extracting Bacillus anthracis Sterne spores from commonly used wipe sampling materials and to describe performance using the interfacial energy concept. In addition, surface thermodynamics was applied to understand and predict surface sampling performance. Wipe materials were directly inoculated with known concentrations of B. anthracis spores and placed into extraction solutions, followed by sonication or vortexing. Experimental factors investigated included wipe material (polyester, cotton, and polyester-rayon), extraction solution (sterile deionized water [H(2)O], deionized water with 0.04% Tween 80 [H(2)O-T], phosphate-buffered saline [PBS], and PBS with 0.04% Tween 80 [PBST]), and physical dissociation method (vortexing or sonication). The most efficient extraction from wipes was observed for solutions containing the nonionic surfactant Tween 80. The increase in extraction efficiency due to surfactant addition was attributed to an attractive interfacial energy between Tween 80 and the centrifuge tube wall, which prevented spore adhesion. Extraction solution significantly impacted the extraction efficiency, as determined by statistical analysis (P < 0.05). Moreover, the extraction solution was the most important factor in extraction performance, followed by the wipe material. Polyester-rayon was the most efficient wipe material for releasing spores into solution by rank; however, no statistically significant difference between polyester-rayon and cotton was observed (P > 0.05). Vortexing provided higher spore recovery in H(2)O and H(2)O-T than sonication, when all three wipe materials and the reference control were considered (P < 0.05).

Setting risk-informed environmental standards for Bacillus anthracis spores

In many cases, human health risk from biological agents is associated with aerosol exposures. Because air concentrations decline rapidly after a release, it may be necessary to use concentrations found in other environmental media to infer future or past aerosol exposures. This article presents an approach for linking environmental concentrations of Bacillus. anthracis (B. anthracis) spores on walls, floors, ventilation system filters, and in human nasal passages with human health risk from exposure to B. anthracis spores. This approach is then used to calculate example values of risk-informed concentration standards for both retrospective risk mitigation (e.g., prophylactic antibiotics) and prospective risk mitigation (e.g., environmental clean up and reoccupancy). A large number of assumptions are required to calculate these values, and the resulting values have large uncertainties associated with them. The values calculated here suggest that documenting compliance with risks in the range of 10(-4) to 10(-6) would be challenging for small diameter (respirable) spore particles. For less stringent risk targets and for releases of larger diameter particles (which are less respirable and hence less hazardous), environmental sampling would be more promising.