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Effectiveness of Formaldehyde in Various Soil Types as a Wide Area Decontamination Approach for Bacillus anthracis Spores
Citation:
Richter, W., M. Sunderman, Z. Willenberg, Michael Calfee, S. Serre, AND J. Wood. Effectiveness of Formaldehyde in Various Soil Types as a Wide Area Decontamination Approach for Bacillus anthracis Spores. PLOS ONE . Public Library of Science, San Francisco, CA, 17(11):e0277941, (2022). https://doi.org/10.1371/journal.pone.0277941
Impact/Purpose:
The results from the study provide information on the efficacy of using liquid formaldehyde in soil against B.a. and B.g. spores. These data may aid in the selection of appropriate decontamination parameters when using liquid formaldehyde for soil remediation. The results also provide data to support use of B.g. as a surrogate for B.a. spores when decontaminating with formaldehyde solutions.
Description:
Aims: The purpose of this study was to evaluate the decontamination efficacy of liquid formaldehyde solutions in various soil types against spores of Bacillus anthracis (B.a.) and potential surrogate spore Bacillus atrophaeus (B.g.). Methods and Results: B.a. and B.g. were inoculated (approx. 1 x 108 colony forming units) into one of three soil types (sand, loam, or clay), homogenized and allowed to dry for 1-hour. Through a series of six bench-scale experiments, two concentrations (2.5 or 5%) and two volumes (2 or 2.8 mL) of liquid formaldehyde solution were then added to the inoculated soil (8 cm3) and allowed to remain in contact within the soil for 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 detected/recovered from the soil samples) was achieved for B.a. spores using 2.8 mL of 2.5% formaldehyde uncovered, or 2.0 mL of 2.5% formaldehyde covered when assessed after 48 hours of contact. The latter condition also resulted in complete inactivation when evaluated at a colder 10°C temperature and a reduced contact time of 24 hours. Significant effects at the 95% level of confidence were obtained for covered/uncovered, species, and formaldehyde solution volume, demonstrating 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. anthracis Ames. Conclusions: The use of liquid formaldehyde solution (2.5-5%) can provide high level decontamination (>6 log reduction (LR) or complete inactivation) for B.a. spores in soil matrices. Covering the soil after application would allow for less formaldehyde solution to be used without impacting the overall efficacy of the process.
URLs/Downloads:
DOI: Effectiveness of Formaldehyde in Various Soil Types as a Wide Area Decontamination Approach for Bacillus anthracis Spores
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