Occurrence and prevalence of antimicrobial resistance in urban karst groundwater systems based on targeted resistome analysis

Authors: KAISER, RACHEL - Tennessee Technological University; POLK, JASON - Western Kentucky University; DATTA, TANIA - Tennessee Technological University; KEELY, SSCOTT - Us Environmental Protection Agency (EPA); BRINKMAN, NICHOLE - Us Environmental Protection Agency (EPA); Parekh, Rohan; Agga, Getahun

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/27/2023
Publication Date: 3/5/2023
Citation: Kaiser, R.A., Polk, J., Datta, T., Keely, S., Brinkman, N., Parekh, R.R., Agga, G.E. 2023. Occurrence and prevalence of antimicrobial resistance in urban karst groundwater systems based on targeted resistome analysis. Science of the Total Environment. 874. Article 162571. https://doi.org/10.1016/j.scitotenv.2023.162571.
DOI: https://doi.org/10.1016/j.scitotenv.2023.162571

Interpretive Summary: Antimicrobial resistance is a global public health crisis threatening human, animal, and environmental health. In the United States and worldwide, antimicrobial resistance monitoring has focused primarily on human and animal health. However, recently the importance of the environment as a reservoir and route of dissemination is being realized. The One Health approach of managing antimicrobial resistance crisis is getting attention in the interconnected world. More focus is being directed towards monitoring water resources for antimicrobial resistance. Studies were conducted in wastewater treatment plants and surface streams. However, the karst aquifer systems have been overlooked. Karst landscapes provide significant amounts of drinking water. Karst aquifers are vulnerable to surface contaminants such as antimicrobial resistant bacteria. Once introduced into the groundwater system, the contaminants can easily disseminate due to the loose formations under karst landscape. Ten sites representing diverse groundwater features (springs, wells and cave streams) were sampled weekly for 46 weeks. In addition, a primarily groundwater fed river that provides drinking water to the city and downstream communities was sampled. Water samples were analyzed for large and diverse group of antimicrobial resistance genes conferring resistance to publicly important antibiotics and a commonly used disinfectant. Additionally, human and animal markers were tested for source tracking of microbial contamination. The project enabled to understand the impacts of spatial, temporal, land use, feature type and season on the occurrences of antimicrobial resistance genes. Antimicrobial resistance genes were detected throughout the aquifer in all karst feature types and seasons. Antimicrobial resistance genes occurred at higher abundance during the summer and fall seasons. Spring water sources had the highest frequency and abundance of the antimicrobial resistance genes, compared to other sources. Human source was identified as the major contributor of microbial contamination in this urban karst groundwater system. Our study highlighted the importance of karst groundwater system as a reservoir and dissemination route for diverse antimicrobial resistance genes.

Technical Abstract: The development and occurrence of antimicrobial resistance (AMR) is a global health crisis threatening human, animal, and environmental health. Antimicrobial resistance monitoring and management has primarily focused on human and animal health; however, the natural environment, specifically water resources, has been recognized as a reservoir and dissemination pathway for AMR. Surveillance and understanding of AMR in water resources has primarily occurred in wastewater treatment plants and surface streams, overlooking vulnerable karst aquifer systems. Karst landscapes are present on every continent and these aquifer systems provide about 10% of the global population with drinking water; yet, the urbanization impacts on these vulnerable aquifers is often overlooked, specifically for the threat of AMR. This study used high-throughput qPCR to determine the occurrence of urban-related antimicrobial resistant genes (ARG) in Bowling Green, KY, a developing urban karst groundwater system. Ten sites throughout the city were sampled weekly and analyzed for the occurrence and relative abundance of 85 ARGs, as well as seven microbial source tracking (MST) genes, providing a spatiotemporal understanding of the AMR threat in urban karst groundwater. To further understand AMR in this environment, potential drivers (landuse, karst feature type, season, MST markers) were considered in relation to the resistome relative abundance. A constant occurrence of all targeted ARGs were detected throughout the aquifer regardless of karst feature type or season, specifically for sulfonamide (sul1), quaternary ammonium compound (qacE), and aminoglycoside (strB) antimicrobial classes. Higher occurrence and relative abundance were detected during the summer and fall seasons, as well as at the spring features. Karst feature type had the greatest influence on AMR. This is one of the first studies to extensively define an urban karst groundwater resistome and these findings can contribute to the development of effective management and mitigation strategies for AMR to ensure the protection of human health.