Recovery efficiencies for Burkholderia thailandensis from various aerosol sampling media

Abstract

Burkholderia thailandensis is used in the laboratory as a surrogate of the more virulent B. pseudomallei. Since inhalation is believed to be a natural route of infection for B. pseudomallei, many animal studies with B. pseudomallei and B. thailandensis utilize the inhalation route of exposure. The aim of the present study was to quantify the recovery efficiency of culturable B. thailandensis from several common aerosol sampling devices to ensure that collected microorganisms could be reliably recovered post-collection. The sampling devices tested included 25 mm gelatin filters, 22 mm stainless steel disks used in Mercer cascade impactors, and two types of glass impingers. The results demonstrate that while several processing methods tested resulted in significantly lower physical recovery efficiencies than other methods, it was possible to obtain culturable recovery efficiencies for B. thailandensis and physical recovery efficiencies for 1 μm fluorescent spheres of at least 0.95 from all of the sampling media tested given an appropriate sample processing procedure. The results of the present study also demonstrated that the bubbling action of liquid media in all-glass impingers (AGIs) can result in physical loss of material from the collection medium, although additional studies are needed to verify the exact mechanisms involved. Overall, the results of this study demonstrate that the collection mechanism as well as the post-collection processing method can significantly affect the recovery from and retention of culturable microorganisms in sampling media, potentially affecting the calculated airborne concentration and any subsequent estimations of risk or dose derived from such data.

Keywords: Burkholderia thailandensis; aerosol; aerosol sampling; culturable recovery efficiency; inhalation; physical recovery efficiency.

Figure 1

Physical recovery efficiency of 1 μm fluorescent melamine beads from 25 mm gelatin filters. The physical recovery efficiency of fluorescent beads from gelatin filters following 3 min of vortexing in room temperature water was significantly less than the other three processing methods (P < 0.0001); lines represent the mean, and ± one standard deviation; n = 10 for each processing method.

Figure 2

Physical recovery efficiency of 1 μm fluorescent melamine beads from 22 mm stainless steel disks. The physical recovery efficiency of fluorescent beads from stainless steel disks was significantly different for all three processing methods tested (P < 0.0001); lines represent the mean, and ± one standard deviation; n = 10 for each method.

Figure 3

Physical recovery and retention efficiencies of 1 μm fluorescent melamine beads from impinger jars. Top: Physical recovery efficiency; n = 10 for each jar type; Bottom: Physical retention efficiency; n = 9 for SKC filled with 15 ml; n = 8 for SKC filled with 20 ml; n = 8 for AGI filled with 20 ml; n = 3 for AGI filled with 10 ml; lines represent the mean and ± one standard deviation.

Figure 4

Culturable recovery efficiency of B. thailandensis. The culturable recovery efficiency of B. thailandensis from any of the sampling media and recovery processes tested were not significantly different from one another (P = 0.1569); lines represent the mean, and ± one standard deviation; n = 10 for each jar type.