Effect of Collection Method and Archiving Conditions on the Survivability of Vegetative and Spore Forming Bacteria
Abstract
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.
Citation
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 https : / /hdl .handle .net /1969 .1 /ETD -TAMU -2009 -08 -6965.