Stable spatial patterns of concentrations of antibiotic resistant bacteria in irrigation water

Authors: Stocker, Matthew; SMITH, JACLYN - Oak Ridge Institute For Science And Education (ORISE); Morgan, Billie; PRINN, MATTHEW - Collaborator; Pachepsky, Yakov

Submitted to: Environmental Monitoring and Assessment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/27/2024
Publication Date: 11/29/2024
Citation: Stocker, M.D., Smith, J., Morgan, B.J., Prinn, M.J., Pachepsky, Y.A. 2024. Stable spatial patterns of concentrations of antibiotic resistant bacteria in irrigation water. Environmental Monitoring and Assessment. 13. Article e56. https://doi.org/10.1186/s40068-024-00385-0.
DOI: https://doi.org/10.1186/s40068-024-00385-0

Interpretive Summary: Antibiotic-resistant bacteria can be spread in irrigation water to crops which are later consumed by humans and animals. Determining the concentrations of resistant bacteria is therefore an important research and management task. By taking samples from 20 sites across an irrigation pond on nine dates, we were able to use the empirical orthogonal function (EOF) analysis to detect persistent spatial patterns in the concentrations of tetracycline- and cefotaxime-resistant bacteria. These patterns were used to identify sampling sites which could best represent the average concentrations across the entire waterbody. Examining the patterns also revealed that bank sampling sites contained much higher antibiotic-resistant bacteria levels than interior sites. Additionally, we found that the persistent patterns of antibiotic-resistant bacteria could be predicted from the persistent patterns of water quality parameters. Results of this work will be useful to water quality managers, and researchers in that they can guide the design of monitoring and surveys of irrigation water sources for antibiotic-resistant bacteria.

Technical Abstract: Irrigation waters serve as vectors for the spread of antibiotic-resistant bacteria which presents a worldwide health concern. Determining the concentrations of those bacteria in waters used for irrigation is therefore an important monitoring target. The objective of this work was to determine the existence of persistent spatial patterns in antibiotic-resistant bacteria in an irrigation waterbody and compare the patterns with patterns of water quality parameters. Escherichia coli, total coliforms, and total heterotrophic bacteria concentrations were measured in water samples collected from 20 sites across an irrigation waterbody on nine sampling dates. The Empirical Orthogonal Function (EOF) analysis was used to detect persistent spatial patterns of tetracycline- and cefotaxime-resistant bacteria as well as water quality parameters. The average concentrations of both generic and antibiotic-resistant bacteria were an order of magnitude higher in bank sampling sites than interior sites. From the EOF analysis results, sampling locations were identified which could provide the best estimates of the average concentrations for each bacterial group. Patterns in temperature (rs = -0.638 to -0.749), dissolved oxygen (rs = -0.173 to -0.675), and pH (rs = -0.483 to -0.770) showed the strongest negative correlations with patterns in bacteria concentrations while all other water quality patterns tended to be positively correlated. The EOF analysis proved to be effective for identifying representative sampling locations for the measurement of antibiotic resistant bacteria in irrigation water sources.