Abstract
Sampling to determine the presence of Bacillus anthracis spores in an environment is important for determining extent of contamination, assessing risk for exposure and need for medical treatment, and especially for guiding clean-up and re-entry efforts. There are currently no validated methods specifically for collecting and analyzing B. anthracis spores in environmental samples. In this investigation, samples were collected in a U.S. Postal facility in Washington, DC which was known to be extensively contaminated with B. anthracis spores. One of the objectives of this survey was to compare the relative effectiveness of surface swab, wipe, and HEPA vacuum samples for collecting spores from contaminated surfaces. The results of this side-by-side comparison of swab (wet and dry), wipe, and HEPA vacuum samples on non-porous surfaces indicated good agreement between the HEPA vacuum and wipe samples. However, the HEPA vacuum sock and wipe samples agreed poorly with the swab samples. The dry swabs performed especially poorly, failing to detect spores over two thirds of the time when they were detected by wipe and HEPA vacuum samples. This data indicate that dry swabs should be not be used as a sampling procedure for B. anthracis spores. The wipe samples collected following HEPA vacuum samples and the HEPA vacuum samples following wipe samples indicated that neither of these sampling methods completely removed spores from the sampled surfaces. This study provides evidence for the need to quantify sampling efficiency to develop the type of "limit of detection data" that are normally created for other types of sampling and analytical methods.
