Distribution of antibiotic resistance in a mixed-use watershed and the impact of wastewater treatment plants on antibiotic resistance in surface water

Authors: CHO, SOHYUN - Oak Ridge Institute For Science And Education (ORISE); Hiott, Lari; Read, Quentin; DAMASHEK, JULIAN - Utica University; WESTRICH, JASON - University Of Georgia; EDWARDS, MARTINIQUE - University Of Georgia; SEIM, ROLAND - Environmental Protection Agency (EPA); GLINSK, DONNA - Environmental Protection Agency (EPA); MCDONALD, JACOB - University Of North Georgia; OTTESEN, ELIZABETH - University Of Georgia; LIPP, ERIN - University Of Georgia; HENDERSON, MATTHEW - Environmental Protection Agency (EPA); Jackson, Charlene; Frye, Jonathan

Submitted to: Antibiotics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/31/2023
Publication Date: 11/2/2023
Citation: Cho, S., Hiott, L.M., Read, Q.D., Damashek, J., Westrich, J., Edwards, M., Seim, R.F., Glinsk, D.A., Mcdonald, J.M., Ottesen, E.A., Lipp, E.K., Henderson, M.W., Jackson, C.R., Frye, J.G. 2023. Distribution of antibiotic resistance in a mixed-use watershed and the impact of wastewater treatment plants on antibiotic resistance in surface water. Antibiotics. 2023(12):1586. https://doi.org/10.3390/antibiotics.
DOI: https://doi.org/10.3390/antibiotics

Interpretive Summary: Surface water serves as a collection place for antibiotic resistance (AR), is an environment for its exchange, and is a vehicle for its dissemination. We performed this study to expand our knowledge on the existing state of AR in the freshwater environment due to the growing concern about the presence of AR contaminants in the environment. We took multiple approaches to evaluate the prevalence, diversity, and sources of AR contaminants in surface water by detecting antibiotics, AR genes, and AR bacteria, including extended-spectrum ß-lactamase (ESBL)-producing Enterobacteriaceae and carbapenem-resistant Enterobacteriaceae (CRE) which are a global health problem. We found that AR contaminants were prevalent and widely distributed in a mixed-use watershed that is representative of much of the land use in the U.S. The widespread occurrence and abundance of medically important antibiotics, pathogenic bacteria, and the genes associated with resistance to these antibiotics, may potentially pose risks to the local populations exposed to these water sources. Furthermore, the removal efficiency of antibiotics and AR genes in wastewater treatment plants (WWTPs) and the impact of WWTP effluents on the levels of AR contaminants in receiving water were investigated. The results showed that WWTPs were not able to completely remove AR contaminants, indicating that WWTPs are a source of AR contaminants in receiving water. However, we found that much of AR contamination was present in streams not associated with known wastewater discharges, suggesting that there are other sources of AR contamination.

Technical Abstract: The aquatic environment has been recognized as a source of antibiotic resistance (AR) that factors into the One Health approach to combat AR. To provide much needed data on AR in the environment, a comprehensive survey of antibiotic-resistant bacteria (ARB), antibiotic resistance genes (ARGs), and antibiotic residues was conducted in a mixed-use watershed and wastewater treatment plants (WWTPs) within the watershed to evaluate these contaminants in surface water. A culture-based approach was used to determine prevalence and diversity of ARB in surface water. Low levels of AR Salmonella (9.6%) and Escherichia coli (6.5%) were detected, while all Enterococcus were resistant to at least one tested antibiotic. Fewer than 20% of extended-spectrum _-lactamase (ESBL)-producing Enterobacteriaceae (17.3%) and carbapenem-resistant Enterobacteriaceae (CRE) (7.7%) were recovered. Six ARGs were detected using qPCR, primarily the erythromycin-resistance gene, ermB. Of the 26 antibiotics measured, almost all water samples (98.7%) had detectable levels of antibiotics. Analysis of wastewater samples from three WWTPs showed that WWTPs did not completely remove AR contaminants. ARGs and antibiotics were detected in all the WWTP effluent discharges, indicating that WWTPs are the source of AR contaminants in receiving water. However, no significant difference in ARGs and antibiotics between the upstream and downstream water suggests that there are other sources of AR contamination. The widespread occurrence and abundance of medically important antibiotics, bacteria resistant to antibiotics used for human and veterinary purposes, and the genes associated with resistance to these antibiotics, may potentially pose risks to the local populations exposed to these water sources.