Date of Award
Spring 2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Civil, Construction, and Environmental Engineering
First Advisor
Patrick McNamara
Second Advisor
Walter McDonald
Abstract
Antibiotic resistance in the environment poses significant risks to human health, especially through the transmission of antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARB) via pathways like food and water. Urban stormwater runoff has been identified as a significant contributor to the release and transport of ARGs in the environment but has remained under-researched. This dissertation aimed to address this gap by investigating the fate of ARGs in urban stormwater runoff to guide future stormwater management decisions. Two phases were completed; the first sought to investigate extracellular antibiotic resistance genes (eARGs) in stormwater runoff, and the second focused on quantifying the impact of stormwater on surface waters and green stormwater infrastructure (GSI). This dissertation first investigated a component of antibiotic resistance research that was severely understudied: eARGs. A method was developed to extract and quantify the abundance and diversity of eARGs. The findings unveiled variations in the fate of eARGs comparatively to intracellular ARGs (iARGs) in stormwater runoff. Specifically, the iARG and eARG resistomes displayed distinct differences in composition. Conclusively, this research emphasized the significance of eARGs as a unique component in the environmental resistome, crucial for assessing the threat of antibiotic resistance from stormwater runoff. Following, the impact of stormwater runoff on downstream resistomes was assessed. Stormwater was concluded to propagate resistance in surface waters through the pollutants it contains and its resistome. Specifically, heavy metals and nutrients increased ARG and ARB concentrations and stormwater introduced a unique resistome to surface water, causing a lasting change in diversity beyond the initial rainfall event. A GSI bioretention cell reduced ARG concentration 30% and altered the diversity of ARGs in stormwater. GSI soils were also discovered to accumulate ARGs at elevated concentrations compared to nonengineered soils. Importantly, the shifts in the resistome observed between the influent and the effluent of the GSI system led to less of an impact on the resistome of surface water. The observed modifications in the resistome profiles indicate a crucial role for GSI in reducing the spread of antibiotic resistance through urban water cycle.