Research roundup: Study aims to map, predict antimicrobial hotspots in Minnesota

November 22, 2021

As long as there have been antibiotics—coming up on 100 years now—genes have adapted to sidestep them. Today, the Centers for Disease Control calls antibiotic (or antimicrobial) resistance (AMR) “one of the biggest public health challenges of our time,” responsible for 2.5 million infections and more than 35,000 human deaths in the U.S. each year. It affects animals with relative equity. 

Antimicrobials and antimicrobial-resistance genes (ARG) in the natural environment have been well studied, but how those findings relate to point sources like wastewater treatment facilities, hospitals, and animal farms have not. Now, a team of University researchers led by Irene Bueno Padilla, MV, MPH, PhD, and Randy Singer, DVM, PhD, have set out to quantify and predict antimicrobials and ARG in water and in sediment at the bottom of water bodies via spatial mapping at both macro- and microscale. The team used Minnesota as its mapping template. 

A graphic showing antimicrobial concentrations for main antimicrobials detected in sampling sites in 2018 (water) and 2019 (water and sediment)Over the course of two summers the team tested samples throughout the state and ran predictive models in the absence of samples. At the statewide macro level they found the highest concentrations across all antimicrobial classes were found near populated areas. At the microscale, where the team took samples from specific bodies of water near point sources, they found wastewater treatment facilities had an effect on ARG abundance but not on antimicrobial concentrations. However, they found significantly higher levels of several antimicrobial-resistance genes right near wastewater discharge points compared to points down- or upstream. They noted that results pulled from sediment samples reflect a historical record of antimicrobials and ARG in those areas, where those pulled from water reflect a more transient record by virtue of flowage.  

Additional sampling locations, coupled with more knowledge of how frequently and where geographically antibiotics are prescribed to animals and humans, will improve predictive models and methods for future studies, the researchers say. 

The scientists published their findings in the journal Scientific Reports in September. Meantime, the researchers hope this study—funded by the Minnesota Environmental and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources—can contribute to the design of an environmental monitoring approach to advance collective understanding of AMR persistence and dissemination.

Providing critical collaboration on the study were William A. Arnold, PhD, and Timothy LaPara, PhD, in the University's Department of Civil, Environmental, and Geo- Engineering; Kristine Wammer, PhD, of the University of St. Thomas; and Amanda Beaudoin, PhD, at the Minnesota Department of Health.



A view from a bluff overlooking a northern Minnesota lake on a sunny September day.
Mike Oakes
A view from above of a northern Minnesota lake