Effect of Deposition Methods (Pipette vs Aerosol) on the Amount of Transfer of DNA attached Polystyrene Latex Bead

Maria King, Jana Kesavan, VIOLETTE RAMIREZ, Texas A&M University

     Abstract Number: 216
     Working Group: Aerosol Science of Infectious Diseases: What We Have Learned and Still Need to Know about Transmission, Prevention, and the One Health Concept

Abstract
Contact transfer of bacteria from fomite can spread diseases and it is important to quantify the amount for risk calculations and for decontamination of surfaces. Controlled laboratory studies can be conducted using bacteria but realistic outdoor tests may require surrogates. DNA attached 1 micrometer Polystyrene Latex microspheres (DNA-PSL) may be a good bacteria surrogate because of the particle size and detection of low concentrations. Pipetting is the common method used in depositing particles onto surfaces; however, this may not represent aerosol deposition such as cough droplets falling onto surfaces. This study evaluated the effect of deposition methods (pipette vs aerosol) on the transfer efficiency (TE) of DNA-PSL. Aluminum, formica and glass slides were selected as test surfaces. A commercial-mesh nebulizer was used to aerosolize liquid at 1 ml/min into a sealed 27 L polypropylene and polyethylene chamber. Pipetted samples were distributed in 80 µL aliquots across the surface. The amount of transfer was determined by wiping the slide with 1.5 in2 parafilm and analyzing the samples. TE of particles was determined by comparing the amount of particulate matter recovered from parafilm to the original deposited amount. Real-time polymerase chain reaction was performed to quantify the amount of DNA in samples. The transfer efficiency of pipetted surface samples at 20% relative humidity (RH) was 5%±1.25% (glass,), 4%±1.25% (aluminum), and 5%±1.34% (formica). At 80% RH higher efficiencies were obtained: 9%±0.13% (glass), 5%±1.75% (aluminum) and 9%±0.36% (formica). For aerosol deposited surface samples at 20% RH, TE was 15%±0.29% (glass), 15%±0.09% (aluminum), and 16%±0.60% (formica). At 80% RH, the values were 14%±0.79% (glass), 13%±0.013% (aluminum) and 15%±0.77% (formica). The TE for pipetted samples was lower compared to aerosolized material. Elevated RH resulted in higher TE for pipetted samples, however, no significant difference was detected for the aerosolized samples.