Optimizing the Recovery of Surrogates for Bacterial Bioterrorism Agents from Ventilation Filters

Heating, ventilating, and air‐conditioning (HVAC) filters have the potential to serve as long‐term integrated samplers for biological particles that may be released intentionally or unintentionally into a public building. Methods for eluting bacteria that are surrogates for potential bioterrorism agents from HVAC filters were tested for their ability to recover as high a percentage of culturable bacteria as possible. A solution of 0.02% Tween‐80 in water was an effective eluent for Bacillus globigii (BG) spores whereas phosphate‐buffered saline was the most effective eluent for vegetative bacteria. Hand shaking was a more effective agitation method for high recovery rates than vortexing or mechanical shaking. The results indicate that BG spores can be eluted successfully while maintaining essentially 100% culturability. The recovery of the vegetative bacteria Mannheimia haemolytica and Yersinia ruckeri was 80% or higher under optimal conditions. The culturability of the vegetative bacteria eluted from HVAC filters declined substantially within as little as 2 h after the bacteria were loaded onto the filter. The culturability of the BG spores eluted from filters exhibited an exponential decay subsequent to loading with a half‐life of 8–9 days.