Funding Agency: U.S. Department of Agriculture, National Institute of Food and Agriculture

Collaborators: Adina Howe (Iowa State University); Michelle Soupir (Iowa State University); Daniel Anderson (Iowa State University)

Project Description: Elevated levels of antimicrobials, antibiotic-resistant bacteria (ARB), and antibiotic resistance genes (ARG) enter the environment through land application of manure from animal production facilities. Over 15.6 million kilograms of veterinary antimicrobials are sold annually in the United States for livestock disease control and growth promotion. Because 50-100% of administered antimicrobials can pass through animals unmetabolized, large amounts of residues enter the environment with manure and remain in the soil due to limited degradation. These residues can promote the development and spread of ARB and ARG within the soil microbiome. Additionally, metals have been linked to higher ARG levels in soil and manure, thereby further strengthening the selection of resistance. The increase in ARB and ARG poses health risks to humans through possible exposure to contaminated food or water.            

The objectives of the study are to: Conduct research aimed at reducing antimicrobial resistance (AMR) in agroecosystems by: (1) Developing improved tools to indicate AMR risk in agricultural environments; (2) Identifying best practices to mitigate AMR during manure storage and treatment; and (3) Advancing mechanistic understanding of how AMR evolves during swine manure management.

Recent Related Publications:

1. Bajracharya, P.; Radmer, L.; Lee, J.; Ríos-Bonilla, K. M.; Aga, D. S.; Soupir, M. L.; Andersen, D. S.; *Howe, A. Evaluation of Effectiveness of Swine Manure Treatment Alternatives to Mitigate Antimicrobial Resistance. Journal of the ASABE. 2025. 68(6): 969-979.
2. *Alt, L.; Craig, A.; Congilosi, J.; Aga, D.; Howe, A.; Soupir, M. Transport of Antibiotics, Antibiotic Resistant Bacteria, and Antibiotic Resistance Genes Through Prairie Strips During Simulated Runoff. Journal of Natural Resources and Agricultural Ecosystems. 2024. 2(4):167-178.
3. Congilosi, J.; Wallace, J.; Neher, T.; Howe, A.; Soupir, M.; *Aga, D. Co-occurrence of antimicrobials and metals as potential drivers of antimicrobial resistance in swine farms. Frontiers in Environmental Science. 2022. 10:1018739. 
4. Congilosi, J. L.; *Aga, D. S. Review on the fate of antimicrobials, antimicrobial resistance genes, and other micropollutants in manure during enhanced anaerobic digestion and composting. Journal of Hazardous Materials. 2021. 405:123634.

Related Publications:

1. Hurst, J. J. et al. Trends in Antimicrobial Resistance Genes in Manure Blend Pits and Long-Term Storage Across Dairy Farms with Comparisons to Antimicrobial Usage and Residual Concentrations. Environ. Sci. Technol. 53, 2405–2415 (2019).

2. Wallace, J. S. & Aga, D. S. Enhancing Extraction and Detection of Veterinary Antibiotics in Solid and Liquid Fractions of Manure. J. Environ. Qual. 45, 471–479 (2016).

3. Wallace, J. S., Garner, E., Pruden, A. & Aga, D. S. Occurrence and transformation of veterinary antibiotics and antibiotic resistance genes in dairy manure treated by advanced anaerobic digestion and conventional treatment methods. Environ. Pollut. 236, 764–772 (2018).

4. Hurst, J. J., Wallace, J. S. & Aga, D. S. Method development for the analysis of ionophore antimicrobials in dairy manure to assess removal within a membrane-based treatment system. Chemosphere 197, 271–279 (2018).

5. Aga, D. S. et al. Challenges in the Measurement of Antibiotics and in Evaluating Their Impacts in Agroecosystems: A Critical Review. J. Environ. Qual. 45, 407–419 (2016).

6. Wallace, J. S., Garner, E., Pruden, A. & Aga, D. S. Occurrence and transformation of veterinary antibiotics and antibiotic resistance genes in dairy manure treated by advanced anaerobic digestion and conventional treatment methods. Environ. Pollut. 236, 764–772 (2018).