Non-point human fecal contamination from aging wastewater infrastructure is a primary driver of antibiotic resistance in surface waters

Authors: DAMASHEK, JULIAN - University Of Georgia; WESTRICH, JASON - University Of Georgia; BATEMAN, JACOB - University Of Georgia; TEACHEY, MORGAN - University Of Georgia; Jackson, Charlene; Frye, Jonathan; LIPP, ERIN - University Of Georgia; CAPPS, KRISTA - University Of Georgia; OTTESEN, ELIZABETH - University Of Georgia

Submitted to: Water Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/9/2022
Publication Date: 7/11/2023
Citation: Damashek, J., Westrich, J.R., Bateman, J.M., Teachey, M.E., Jackson, C.R., Frye, J.G., Lipp, E.K., Capps, K.A., Ottesen, E.A. 2023. Non-point human fecal contamination from aging wastewater infrastructure is a primary driver of antibiotic resistance in surface waters. Water Research. https://doi.org/10.1016/j.watres.2022.118853.
DOI: https://doi.org/10.1016/j.watres.2022.118853

Interpretive Summary: Antibiotic resistance is a threat to human health. How the genes that cause antimicrobial resistance are transferred in the environment is poorly understood. Many surface water resources in the environment are thought to be hot-spots for the transfer of antimicrobial resistance genes (ARGs). Agricultural runoff and human waste are known sources of antimicrobial resistance genes (ARGs) in aquatic systems. To investigate this, genetic markers of fecal source genes and ARGs were quantified in water samples (n=992) collected each season over a 5-year period from 115 sites in the Upper Oconee watershed (Georgia, USA). This area is characterized by gradients of agricultural and urban development. Widespread fecal contamination was found from human (48% of samples), ruminant (55%), and poultry (19%) sources. In addition, 73% of samples tested positive for at least one of the six targeted ARGs. ARGs were strongly correlated with human fecal genes, however, many highly contaminated samples were not associated with sewage outfalls, an expected source of fecal and ARG pollution. To determine sources of fecal and ARG contamination, we combined ARG and fecal marker data with geospatial data on land use/land cover and wastewater infrastructure across the watershed. This analysis found strong correlations of ARGs with sewer density and septic system age. This indicates non-point sources of fecal contamination from aging wastewater infrastructure can be critical sources of environmental ARGs.

Technical Abstract: Antibiotic resistance is a global threat to human health. Many surface water resources are environmental hotspots of antibiotic resistant gene (ARG) transfer, with agricultural runoff and human waste both highlighted as sources of ARGs in aquatic systems. Here we quantified fecal marker genes and ARGs in 992 stream water samples collected seasonally during a 5-year period from 115 sites across the Upper Oconee watershed (Georgia, USA), an area characterized by gradients of agricultural and urban development. Widespread fecal contamination was found from human (48% of samples), ruminant (55%), and poultry (19%), and 73% of samples tested positive for at least one of the six targeted ARGs. While ARGs were strongly correlated with human fecal genes, many highly contaminated samples were not associated with sewage outfalls, an expected source of fecal and ARG pollution. To determine sources of fecal and ARG contamination, we synthesized ARG and fecal marker data with geospatial data on land use/land cover and wastewater infrastructure across the watershed. This novel analysis found strong correlations between ARGs and measures of sewer density, sewer length, and septic system age within sample watersheds, indicating non-point sources of fecal contamination from aging wastewater infrastructure can be critical disseminators of environmental ARGs.