Citation:

Cho, S., L. Hiott, Q. Read, J. Damashek, J. Westrich, M. Edwards, R. Seim, D. Glinski, J. Bateman McDonald, E. Ottesen, E. Lipp, Matthew Henderson, C. Jackson, AND J. Frye. Distribution of Antibiotic Resistance in a Mixed-Use Watershed and the Impact of Wastewater Treatment Plants on Antibiotic Resistance in Surface Water. The Journal of Antibiotics. Springer Nature, New York, NY, 12(11):1586, (2023). https://doi.org/10.3390/antibiotics12111586

Impact/Purpose:

This study endeavored to provide an overall picture of AR, including ARB, ARGs, and antibiotics, in a mixed-use watershed thereby shedding light on the possible health impacts that US residents are exposed to through agricultural, municipal, and recreational uses of surface water.  The current study has shown that antibiotic-related contaminants are prevalent in the freshwater environment, including commensal and pathogenic bacteria that are resistant to antibiotics used for human and veterinary purposes, medically important antibiotics, as well as the genes associated with resistance to these antibiotics. The widespread occurrence and abundance of such AR contaminants may potentially pose risks to the local populations exposed to these water sources. ESBL-, AmpC-, and carbapenemase- producing Enterobacteriaceae, which are increasingly reported in healthcare and community settings, were commonly found in surface water and wastewater effluents that were released into this water, indicating their prevalence in the community as well as the natural environment. The comparison of wastewater influent and effluent samples has shown that wastewater treatment is not effective in removing all the AR contaminants present in the wastewater and, in fact, some antibiotics and resistance genes were enriched during the process. Treated effluents carried considerable levels of these AR contaminants, indicating that WWTPs are a relevant source of AR in the receiving water. However, surface water samples that had not been impacted by WWTPs also had high levels of AR contaminants, suggesting that WWTPs are not the sole contributors of AR in the environment, and other sources of AR contaminants should also be considered. In our subsequent study, we will investigate the factors that could have led to high prevalence and widespread distribution of AR contaminants in the water.

Description:

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 β-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.

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