Kassab, Asmaa S. (2009-08). Effect of Collection Method and Archiving Conditions on the Survivability of Vegetative and Spore Forming Bacteria. Master's Thesis. Thesis uri icon

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.
  • 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.

publication date

  • August 2009