Modified Cascade Impactor for Liquid Collection and Increased Sampling Time

JANA KESAVAN, Daniel Mcgrady, Jerold Bottiger, U.S. Army DEVCOM Chemical Biological Center

     Abstract Number: 447
     Working Group: Bioaerosols

Abstract
It is essential to have the capability to size selectively sample bioaerosols for long duration and analyze the collected samples using various methods. However, currently available samplers do not have this capability. Therefore, we modified a cascade impactor for sample collection on wet filters and for long duration sampling. Collection petri dishes with agar were replaced with petri dishes with porous polyethylene plastic disks and collection liquid. A filter was placed on top of the disk for particle collection by impaction. This setup allowed organism collection for 1-4 hours which depended on the environmental conditions. The sample time can be increased by adding collection liquid to the petri dishes as the liquid evaporates. This method allowed for organisms to be collected on wet filters, recovered into liquid and analyzed by PCR, culturing, immunoassay, etc. The polyethylene plastic disks can be autoclaved in between tests for decontamination. Tests with pipetted organisms and 2.5 hours of sampling indicated that when 1.1E5 cfu/stage was observed in the modified cascade impactor, the agar filled plates were dry and no organisms were observed after incubation. Our studies indicated that the modified cascade impactor allowed for long term, size selective sampling that allowed for the use of various sample analysis techniques.