Open AccessRecovery Efficiency and Limit of Detection of Aerosolized Bacillus anthracis Sterne from Environmental Surface Samples
Author(s) -
Cheryl Fairfield Estill,
Paul A. Baron,
Jeremy K. Beard,
Misty J. Hein,
Lloyd D. Larsen,
Laura Rose,
Frank Schaefer,
Judith Noble-Wang,
Lisa Hodges,
Heather Lindquist,
Gregory J. Deye,
Matthew J. Arduino
Publication year - 2009
Publication title -
applied and environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.552
H-Index - 324
eISSN - 1070-6291
pISSN - 0099-2240
DOI - 10.1128/aem.02549-08
Subject(s) - bacillus anthracis , aerosolization , contamination , environmental science , sampling (signal processing) , spore , detection limit , coefficient of variation , chemistry , chromatography , biology , microbiology and biotechnology , optics , physics , ecology , genetics , detector , bacteria , inhalation , anatomy
After the 2001 anthrax incidents, surface sampling techniques for biological agents were found to be inadequately validated, especially at low surface loadings. We aerosolizedBacillus anthracis Sterne spores within a chamber to achieve very low surface loading (ca. 3, 30, and 200 CFU per 100 cm2 ). Steel and carpet coupons seeded in the chamber were sampled with swab (103 cm2 ) or wipe or vacuum (929 cm2 ) surface sampling methods and analyzed at three laboratories. Agar settle plates (60 cm2 ) were the reference for determining recovery efficiency (RE). The minimum estimated surface concentrations to achieve a 95% response rate based on probit regression were 190, 15, and 44 CFU/100 cm2 for sampling steel surfaces and 40, 9.2, and 28 CFU/100 cm2 for sampling carpet surfaces with swab, wipe, and vacuum methods, respectively; however, these results should be cautiously interpreted because of high observed variability. Mean REs at the highest surface loading were 5.0%, 18%, and 3.7% on steel and 12%, 23%, and 4.7% on carpet for the swab, wipe, and vacuum methods, respectively. Precision (coefficient of variation) was poor at the lower surface concentrations but improved with increasing surface concentration. The best precision was obtained with wipe samples on carpet, achieving 38% at the highest surface concentration. The wipe sampling method detectedB. anthracis at lower estimated surface concentrations and had higher RE and better precision than the other methods. These results may guide investigators to more meaningfully conduct environmental sampling, quantify contamination levels, and conduct risk assessment for humans.