Use of a Foam Spatula for Sampling Surfaces after Bioaerosol Deposition

Abstract

The present study had three goals: (i) to evaluate the relative quantities of aerosolized Bacillus atrophaeus spores deposited on the vertical, horizontal top, and horizontal bottom surfaces in a chamber; (ii) to assess the relative recoveries of the aerosolized spores from glass and stainless steel surfaces with a polyester swab and a macrofoam sponge wipe; and (iii) to estimate the relative recovery efficiencies of aerosolized B. atrophaeus spores and Pantoea agglomerans using a foam spatula at several different bacterial loads by aerosol distribution on glass surfaces. The majority of spores were collected from the bottom horizontal surface regardless of which swab type and extraction protocol were used. Swabbing with a macrofoam sponge wipe was more efficient in recovering spores from surfaces contaminated with high bioaerosol concentrations than swabbing with a polyester swab. B. atrophaeus spores and P. agglomerans culturable cells were detected on glass surfaces using foam spatulas when the theoretical surface bacterial loads were 2.88 ؋ 10 4 CFU and 8.09 ؋ 10 6 CFU per 100-cm 2 area, respectively. The median recovery efficiency from the surfaces using foam spatulas was equal to 9.9% for B. atrophaeus spores when the recovery was calculated relative to the theoretical surface spore load. Using a foam spatula permits reliable sampling of spores on the bioaerosol-exposed surfaces in a wide measuring range. The culturable P. agglomerans cells were recovered with a median efficiency of 0.001%, but staining the swab extracts with fluorescent dyes allowed us to observe that the viable cell numbers were higher by 1.83 log units than culturable organisms. However, additional work is needed to improve the analysis of the foam extracts in order to decrease the limit of detection of Bacillus spores and Gram-negative bacteria on contaminated surfaces.Surface sampling is performed on a frequent basis in all situations where clean environment monitoring is needed, e.g., in health care facilities and in the pharmaceutical industry and food industry. An anthrax bioterrorist event in the fall of 2001 has emphasized the importance of efficient sampling methods for detection of pathogenic microorganisms on surfaces within intentionally contaminated locations (22). Unfortunately, our knowledge on the most effective sampling methodology as well as the level of confidence we may have in the results obtained by wiping, swabbing, and other sample collection strategies is still limited (1). Moreover, in most of the studies performed so far, bacteria and/or spores were collected from test samples or coupons of various materials, inoculated with a suspension of microorganisms that had been placed and spread over the surface, and then dried (14, 15). This may not mimic the true situation of surface contamination by a pathogen that has been intentionally released. Edmonds et al. (12) recently reported lower swabbing efficiencies of different types of swab materials used for sampling glass, polycarbonate, and vinyl surfaces contaminat...

Decontamination of Bioaerosols within Engineering Tolerances of Aircraft Materials

“…Additionally, re-aerosolization of spores during these samples was an issue, especially at the lower levels (Baron et al, 2008). Lewandowski et al (2010) evaluated Bacillus atrophaeus to determine the recovery efficiencies from glass and stainless steel surfaces using polyester swab and macrofoam sponge wipe. They found that swabbing with a macrofoam sponge wipe was more efficient in recovering spores from surfaces contaminated with high bioaerosol concentrations than swabbing with a polyester swab.…”

“…Bacillus atrophaeus spores have been used in several studies as well (Brown et al, 2007a;Carrera et al, 2005;Kesavan, 2008;Lewandowski et al, 2010;Martin and Moore, 2001;Thomas et al, 2008;).…”

“…Some of the Bacillus subtilis species were actually renamed a new strain, Bacillus atrophaeus subsp globigii (Burke et al, 2004). Again, there are several tests and studies which have used Bacillus atropheaus (Brown et al, 2008a;Carrera et al, 2005;Kesavan, 2008;Lewandowski et al, 2010;Martin and Moore, 2001;Thomas et al, 2008;). …”

“…Some have stated that there was no method to estimate the actual number that settle on a 100 cm 2 coupon during experiments and that the recovery had to be based on the theoretical number that might deposit. Using that method, overall recovery efficiencies have been as low as 0.9% (Lewandowski et al, 2010). Wagner et al (2008) collected swab surface samples and vortexed each sample for 10 seconds, followed by a serial dilution and plating to TSA.…”

“…Brown et al (2007aBrown et al ( , 2007bBrown et al ( , 2007c Other chambers have been constructed from aluminum to study different aerosol depositions (Byrne et al, 1995;Feather and Chen, 2003;Lai et al, 2002). Lewandowski et al (2010) constructed a test chamber made clear cast acrylic with an interior volume of 0.5 m 3 and bottom surface area was 89 cm wide by 74 cm wide. Several other researchers have constructed 112 chambers over 1 m 3 in volume Marple and Rubow, 1983;Kenny et al, 1999;Koch et al, 1999).…”