Evaluation of sampling methods for Bacillus spore-contaminated HVAC filters

Abstract

The objective of this study was to compare an extraction-based sampling method to two vacuum-based sampling methods (vacuum sock and 37 mm cassette filter) with regards to their ability to recover Bacillus atrophaeus spores (surrogate for Bacillus anthracis) from pleated heating, ventilation, and air conditioning (HVAC) filters that are typically found in commercial and residential buildings. Electrostatic and mechanical HVAC filters were tested, both without and after loading with dust to 50% of their total holding capacity. The results were analyzed by one-way ANOVA across material types, presence or absence of dust, and sampling device. The extraction method gave higher relative recoveries than the two vacuum methods evaluated (p ≤ 0.001). On average, recoveries obtained by the vacuum methods were about 30% of those achieved by the extraction method. Relative recoveries between the two vacuum methods were not significantly different (p > 0.05). Although extraction methods yielded higher recoveries than vacuum methods, either HVAC filter sampling approach may provide a rapid and inexpensive mechanism for understanding the extent of contamination following a wide-area biological release incident.

Considerations for estimating microbial environmental data concentrations collected from a field setting

“…Sampling of heating, ventilation, and air conditioning (HVAC) filters has also been recommended as a method to help determine indoor extent of contamination. 25 , 27 , 28 , 29 …”

Bacillus subtilis biofilm formation under extreme terrestrial and simulated extraterrestrial conditions

“…Spores function as DNA-carrying vectors which support the dispersion and spreading of the species. Spore-containing dust, for example, can be transported over long distances by air or on animal skin and fur (Heyndrickx, 2011, Calfee et al, 2014, Alekhova et al, 2015, Tena et al, 2007. In addition, spores are able to survive the gastrointestinal passage of animals and can therefore be distributed via feces (Hoa et al, 2001).…”

“…In addition, spores are able to survive the gastrointestinal passage of animals and can therefore be distributed via feces (Hoa et al, 2001). B. subtilis spores have been found in the air (Calfee et al, 2014), soil, in water as well as on surfaces within cleanrooms or the ISS (Alekhova et al, 2015, Mahnert et al, 2015. stress levels that can be harmful, the master regulator Spo0A is phosphorylated and if present in high doses can initiate the sporulation, starting with an asymmetric (unipolar) cell division.…”