Evaluation of two surface sampling methods for the detection of Bacillus atrophaeus aerosolized in a test chamber

In response to the airborne release of biothreat agents, surface sampling is often used to provide information on bioaerosol dispersal and deposition, to identify biocontaminant sources, and determine the effectiveness of decontamination. The objective of this project was to use aerosolization and deposition of dry spores to evaluate the efficiency of the cellulose sponge wipe and 37-mm cassette micro vacuum surface sampling methods for the collection of microorganisms from two contaminated surfaces, metal and concrete. Aerosolization trials were performed in a room-sized test chamber with known airborne concentrations of Bacillus atrophaeus spores serving as a surrogate for a bioterrorism agent. Following each aerosolization trial, the chamber heating, ventilation, air conditioning (HVAC) system was turned off to allow airborne spores to settle onto the test materials. Surface sampling was conducted and culture analysis was used to determine the concentration of B. atrophaeus on the surfaces. Results were compared with reference samples to determine the collection efficiency of the sampling methods. The sponge wipe sampling method was significantly more effective than the vacuum method for the collection of B. atrophaeus from both metal and concrete surfaces (P < 0.001). The collection efficiency of the sponge wipe method was 39.5% for metal and 26.5% for concrete, while the collection efficiency of the vacuum method was 7.6% for metal and 9.3% for concrete. The results of this study provided data on the collection efficiencies of two surface sampling methods for detection and enumeration of biocontaminants and can aid in selection of sampling methods.