Date of Award

January 2020

Document Type

Open Access Thesis

Degree Name

Master of Public Health (MPH)


School of Public Health

First Advisor

Melinda Pettigrew


Antimicrobial resistance (AMR) is an emerging public health issue that threatens the efficacy of antibiotic treatment for bacterial infections and human health. Sources of antimicrobial resistance genes (ARGs) in the environment include wastewater treatment plants and animal feeding operations that discharge waste into waterways, such as rivers and streams. This retrospective descriptive study describes the presence of AMR, and specific ARGs in Escherichia coli isolates from two distinct watersheds, rural and urban, with the use of antimicrobial susceptibility testing, whole-genome sequencing (WGS) to detect ARGs, and multi-locus sequence typing. Antimicrobial susceptibility testing was performed for 143 E. coli isolates, 73 originating from a rural watershed and 70 originating from an urban watershed. E. coli isolates from the rural watershed had a significantly higher prevalence of phenotypic non-susceptibility and ARGs for tetracycline (21.9% vs. 2.9%, p < 0.01) when compared to urban watershed isolates. Based on phenotypic-susceptibility testing, WGS data of 68 isolates were annotated for ARGs. These data were used for the prediction of antimicrobial susceptibility, demonstrating high accuracy for the prediction of non-susceptibility for tetracycline, trimethoprim-sulfamethoxazole, and cephalosporins. WGS multi-locus sequence typing (MLST) yielded 47 sequence types, dominated by ST58 (n=6), ST10 (n=5), and ST155 (n=4). Waterways are important reservoirs and disseminators of antimicrobial-resistant bacteria (ARB) and ARGs. The evaluation and monitoring of AMR and ARGs in aquatic environments will lead to improved health through better prevention and control of E. coli infections.


This is an Open Access Thesis.

Open Access

This Article is Open Access