Live-Animal Infectivity Study of a Viable Pathogen Penetrating through a Reactive Filter Medium

RASHELLE S. McDONALD1, Brian K. Heimbuch1, Brenton R. Stone1,2, Michael B. Lore3, Steven H. Hinrichs3, Anthony R. Sambol3, and Joseph D. Wander4 1 Applied Research Associates, Tyndall AFB, FL. 2 Dept. of Environmental Engineering Sciences, U of Florida, Gainesville, FL.,3 Department of Pathology and Microbiology, UNMC 4Airbase Sciences Branch, Air Force Research Laboratory, Tyndall AFB, FL

1 Applied Research Associates, Tyndall AFB, FL. 2 Dept. of Environmental Engineering Sciences, U of Florida, Gainesville, FL.,3 Department of Pathology and Microbiology, UNMC 4Airbase Sciences Branch, Air Force Research Laboratory, Tyndall AFB, FL

     Abstract Number: 807
     Last modified: May 19, 2010

Abstract
Incorporating antimicrobial compounds into filtration media has gained some acceptance in the past decade, but actual benefit to the user is difficult to quantify. Adding the antimicrobial resin poly(styrene-4-[trimethylammonium]methyl triiodide) (PSAI) to N95 filtering facepiece respirators (FFRs) was undertaken commercially as a measure to decrease viable penetration of viruses. Results from in-vitro testing of PSAI-treated FFRs are complicated by chemistry in the aerosol collection system. All-glass impingers containing various fluids are commonly used to collect microbes; however, from different collection media the viability of microbes captured downstream of iodinated media differs by two logs. To skirt this problem and assess the benefit of antimicrobial media downstream, a live-animal aerosol exposure study is necessary. Using the mammalian lung as the collector and detector will provide an empirical measure of the extent to which the complex lung surface interacts with PSAI-exposed microbes to either compete for and neutralize captured iodine or activate the iodine to devitalize the pathogen.
In this exposure study, an infectious bioaerosol is created and flowed through filters containing PSAI or mechanically equivalent untreated filters, then delivered to a panel of animal subjects. CD-1 mice will be exposed to Influenza A H1N1 PR/8/34 virus using the Controlled Aerosol Test System (CATS), which was validated for consistency of aerosol delivery. Following exposure, the mice will be monitored for seven days to assess infection rates. Additionally, a scanning mobility particle sizer will be used to measure particle counts upstream and downstream of the filter and impinger samples will be collected and assayed for viability using a TCID50 assay with Madin–Darby canine kidney cells. Multiple doses will be administered to separate groups of mice by varying the concentration delivered and time of exposure. Dose–response curves will be analyzed to determine the effect of PSAI on infectivity of the microbes post inhalation.