AbstractEmerging outbreaks of airborne pathogenic infections worldwide, such as the current Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) pandemic, have raised the urgency to explain the parameters affecting the survival of airborne microbes in order to develop effective infection control strategies. Conventional techniques for investigating bioaerosol survival in vitro have systemic limitations that prevent the accurate representation of conditions that these particles would experience in the natural environment. Therefore, some basic questions about the fundamental mechanisms influencing the airborne transmission of disease remain unknown.
This thesis describes a laboratory-based approach to explore the synergistic interactions between the physicochemical and biological processes that impact the survival of airborne microorganisms. This novel experimental strategy combines two complementary techniques for probing aerosol particles directly: the CK-EDB (Comparative Kinetics Electrodynamic Balance) and CELEBS (Controlled Electrodynamic Levitation and Extraction of Bio-aerosol onto a Substrate) technologies. Both are based on the electrodynamic levitation of charged droplets and utilize droplet-on-demand dispensers to produce droplets with high monodisperse size distribution. By using the CK-EDB, it is possible to measure the changes in the physicochemical properties of the bioaerosol droplets during and after evaporation with the aim to ultimately interrelate this information to the biological decay responses measured by the CELEBS system.
Therefore, the presented methodology provides a detailed understanding of the processes taking place from aerosol droplet generation through to equilibration and biological decay in the environment, elucidating decay mechanisms not previously described. The impact of evaporation kinetics, solute hygroscopicity and concentration, particle morphology, evaporative cooling, surface enrichment and equilibrium particle size on the airborne survival of microorganisms are reported, using Escherichia coli (MRE-162) as a benchmark microorganism. This new approach can enable direct studies at the interface between aerobiology, atmospheric chemistry, and aerosol physics to determine the main mechanisms of death of airborne pathogens under the unique microphysical properties of the aerosol droplets.
|Date of Award||11 May 2021|
|Supervisor||Jonathan P Reid (Supervisor) & Wuge H Briscoe (Supervisor)|