AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
The Low Cut Point Viable Bioaerosol Collector: Viability of E. coli Samples Collected at 300 L/min and Archived for 15 Days
MARIA D. KING, Ray Pierson, Asmaa Kassab, Texas A&M University
Abstract Number: 195 Working Group: Instrumentation and Methods
Abstract The low cut point 300 L/min Viable Bioaerosol Collector (LCP-VBAC) with an aerosol-to-hydrosol collection efficiency of 63% for 0.49 micrometer PSL particles and ~100% for particles >1 micrometer, was tested in a laboratory with fresh vegetative bacterial cells at the pressure drop of 55”.
Single E. coli cells were nebulized using the Collison 6-jet nebulizer and collected with the LCP-VBAC using 0.01% Tween-20 as collection liquid for 10 min collection periods. To 0.45 mL aliquots of the samples Phosphate Buffer Saline (PBS) was added to 10% final concentration immediately after collection. The third type of sample was collected in 0.01% Tween-20 for five minutes into tubes containing PBS to 10% final concentration. As reference sampler, the SKC Biosampler was used at 12.5 L/min with 20 mL of 0.01% Tween-20. The samples were divided into two equal volumes and stored at room temperature (RT) and 4ºC, respectively, for a period of 15 days. During archiving the culturability of the samples was monitored by plating; and for the samples stored at 4ºC, the DNA intactness was analyzed by real-time PCR. The samples archived at 4ºC for 48 hours in the presence of PBS show 14X recovery in culturability compared to 3X for the samples in Tween-20. Amending the samples with PBS seems to enhance the recovery of culturability; however, at 4ºC it has no significant effect whether the samples are amended with 10% PBS after or during collection. Real-time PCR analysis shows that the cell counts based on DNA content of the as-collected samples are 100X higher than expected based on colony forming units. As time progresses, the difference between DNA-based total cell counts and culturable cell counts decreases to 2X, very likely due to the role of PBS in the restoration of osmotic stress induced cell damage and viability.