Geology topics

Erin E. Silvestri

Publications and source records attributed to Erin E. Silvestri.

5 recordsLinked to original sources

USGS2019

Colony-forming unit spreadplate assay versus liquid culture enrichment-polymerase chain reaction assay for the detection of Bacillus Endospores in soils

A liquid culture enrichment-polymerase chain reaction (E-PCR) assay was investigated as a potential tool to overcome inhibition by chemical component, debris, and background biological impurities in soil that were affecting detection assay performance for soil samples containing Bacillus atrophaeus subsp. globigii (a surrogate for B. anthracis). To evaluate this assay, 9 g of matched sets of three different soil types (loamy sand [sand], sandy loam [loam] and clay) was spiked with 0, ~4.5, 45, 225, 675 and 1350 endospores. One matched set was evaluated using a previously published endospore concentration and colony-forming unit spreadplate (CFU-S) assay and the other matched set was evaluated using an E-PCR assay to investigate differences in limits of detection between the two assays. Data illustrated that detection using the CFU-S assay at the 45-endospore spike level started to become sporadic whereas the E-PCR assay produced repeatable detection at the ~4.5-endospore spike concentration. The E-PCR produced an ~2-log increase in sensitivity and required slightly less time to complete than the CFU-S assay. This study also investigated differences in recovery among pure and blended sand and clay soils and found potential activation of B. anthracis in predominately clay-based soils.

Geosciences↗

USGS2017

Processing protocol for soil samples potentially contaminated with Bacillus anthracis spores [HS7.52.02 - 514]

This protocol describes the processing steps for 45 g and 9 g soil samples potentially contaminated with Bacillus anthracis spores. The protocol is designed to separate and concentrate the spores from bulk soil down to a pellet that can be used for further analysis. Soil extraction solution and mechanical shaking are used to disrupt soil particle aggregates and to aid in the separation of spores from soil particles. Soil samples are washed twice with soil extraction solution to maximize recovery. Differential centrifugation is used to separate spores from the majority of the soil material. The 45 g protocol has been demonstrated by two laboratories using both loamy and sandy soil types. There were no significant differences overall between the two laboratories for either soil type, suggesting that the processing protocol would be robust enough to use at multiple laboratories while achieving comparable recoveries. The 45 g protocol has demonstrated a matrix limit of detection at 14 spores/gram of soil for loamy and sandy soils.

Report↗

USGS2016

Optimization of a sample processing protocol for recovery of Bacillus anthracis spores from soil

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 14 spores/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.

Journal of Microbiological Methods↗

USGS2015

Observations on the migration of bacillus spores outside a contaminated facility during a decontamination efficacy study

The potential for an intentional wide-area or indoor release of Bacillus anthracis spores remains a concern, but the fate and transport of B. anthracis spores in indoor and outdoor environments are not well understood. Some studies have examined the possibility of spore transport within ventilation systems and in buildings and transport into a building following an outdoor release. Little research exists regarding the potential for spores to migrate to the outside of a building following an indoor release. Bacillus species spores have the potential to remain viable in the soil for many years. Lasting environmental contamination following a release is a possibility, and planning for site characterization and remediation activities should consider both indoor-to-outdoor spore transport and outdoor soil as potential exposure pathways.

Journal of Bioterrorism & Biodefense↗

USGS2014

Anthrax and the geochemistry of soils in the contiguous United States

Soil geochemical data from sample sites in counties that reported occurrences of anthrax in wildlife and livestock since 2000 were evaluated against counties within the same states (MN, MT, ND, NV, OR, SD and TX) that did not report occurrences. These data identified the elements, calcium (Ca), manganese (Mn), phosphorus (P) and strontium (Sr), as having statistically significant differences in concentrations between county type (anthrax occurrence versus no occurrence). Tentative threshold values of the lowest concentrations of each of these elements (Ca = 0.43 wt %, Mn = 142 mg/kg, P = 180 mg/kg and Sr = 51 mg/kg) and average concentrations (Ca = 1.3 wt %, Mn = 463 mg/kg, P = 580 mg/kg and Sr = 170 mg/kg) were identified from anthrax-positive counties as prospective investigative tools in determining whether an outbreak had “potential” or was “likely” at any given geographic location in the contiguous United States.

Alabama, California, Colorado, Minnesota, Montana,↗