Date of Award
Fall 2025
Document Type
Open Access Thesis
Department
Environmental Health Sciences
First Advisor
Devin A. Bowes
Abstract
The global threat of antimicrobial resistance (AMR) has been steadily increasing over the past several decades. Consequently, the need to comprehensively assess influential factors of AMR has been prioritized. The overuse and misuse of antibiotics have been identified as a potential population-driver of AMR, however, examining the impacts of antibiotic residue pollution in aquatic environments downstream from communities on human and environmental health has yet to be fully explored. This study aimed to reduce this gap in knowledge by assessing the presence of two broad-spectrum antibiotics (azithromycin and ciprofloxacin) in river water, wastewater effluent, and catfish tissues, and further, explored the human impact of secondary exposure to antibiotic residues via fish consumption. Results revealed that both azithromycin (AZT) and ciprofloxacin (CIP) are measurable (ng/L) in wastewater effluent, catfish tissues, and river water downstream from a local wastewater treatment plant (WWTP) in South Carolina, USA. AZT achieved a 100% detection rate and exhibited higher levels in all three overarching sample types compared to CIP (61.90% detection rate). However, neither antibiotic was detected in the upstream river water sample to the WWTP suggesting that WWTPs may act as a source of antibiotic input into natural waterways. In catfish tissues, a detection rate of 100% and 50% was achieved with concentrations ranging from 61.93-2201.37 ng/kg wet weight and 45.69-61.98 ng/kg wet weight for AZT and CIP, respectively. These measurements were then used to generate an exploratory risk assessment into the concentration of antibiotics a person may consume as a result from recreational fishing. Results from this risk assessment revealed approximately 41-55 ng of AZT and 4.4-5.8 ng of CIP if a person consumed the recommended amount of 6-8 ounces of catfish per week. Understanding the subsequent human health outcomes of chronic, low-level exposure to anthropogenically-sourced antibiotic residues by consuming contaminated catfish and other aquatic species fit for human consumption remain largely uncharacterized. Further research is encouraged that fully examines this relationship in order to inform appropriate public- and environmental-health strategies and improve wastewater treatment processes.
Rights
©2025, Hannah Bruno Malcom
Recommended Citation
Malcom, H. B.(2025). Assessing the Incidence of Antibiotic Residues in Catfish Populations Living in Proximity to Sewage Effluent Discharge Within the Midlands of South Carolina. (Master's thesis). Retrieved from https://scholarcommons.sc.edu/etd/8656