Effect of Collection Method and Archiving Conditions on the Survivability of Vegetative and Spore Forming Bacteria
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To ensure effective detection of bio-particles, it is crucial to understand the effects of collection method and archiving conditions on the survivability of bioaerosols, consequently, the survivability of the spore-forming Bacillus globigii (BG) and MG1655 Escherichia coli (E. coli), was determined after collection. The survivability was defined as the culturable fraction of the archived bacteria/culturable fraction of the as-collected bacteria. The bacteria were aerosolized for up to four days at room temperature (RT, 25 degrees C) and at 4 degrees C and collected in a 100 L/min wetted wall cyclone (WWC) and a 12.5 L/min SKC BioSampler. Aqueous solutions of 0.01% Tween-20 and 30% Ethylene Glycol (EG), with or without 0.5% ovalbumin (OA), were used as the collection fluids. Antifoam B (A-F), at a concentration of 0.2% (V:V) was added to the BG samples containing OA. In general, samples archived at 4 degrees C showed higher survivability than at RT. The survivability were more stable in EG than in Tween-20 especially for BG, very likely due to the surfactant effect of the Tween-20, which would remove the spore coat and initiate germination. In the WWC, adding OA significantly increased the survivability of BG in EG and in Tween-20, especially at RT. Similar effect of OA was found for E. coli samples stored in EG, suggesting that OA might be beneficial in maintaining the survivability. Adding A-F increased the survivability of BG in EG. In the SKC, neither the addition of OA nor A-F seems to have a beneficial effect on the survivability of the spores in EG samples. The best collection fluid for maintaining survivability in the WWC is EG+A-F for BG, and EG+OA for E. coli. However, in the SKC, EG is the best for BG collection and Tween-20 for E. coli. Viability transfer ratios, VTR, (cells surviving collection at time zero/viable cells aerosolized) were calculated for both devices. A performance ratio was calculated as the VTR of the WWC/VTR of the SKC. The geometric mean of the performance ratio is 1.51+/-0.83 for BG and 2.60+/-0.16 for E. coli, indicating that viability transfer ratio of the WWC is typically higher than that of the SKC.
Kassab, Asmaa S. (2009). Effect of Collection Method and Archiving Conditions on the Survivability of Vegetative and Spore Forming Bacteria. Master's thesis, Texas A&M University. Available electronically from