Dietary Impact on Antibiotic Resistance in Feedlot Manure

Report on research conducted at the University of Nebraska, originally printed in the 2021 Nebraska Beef Cattle Report.

Summary

There is a growing public concern regarding antibiotic resistance and the use of antibiotics, including in livestock management. Understanding the ecology of antibiotic resistance among microbes, identifying resistance gene reservoirs, and implementing antibiotic resistance mitigation practices in livestock production is critical to protecting animal and human health while meeting increasing food demands. This research is one of several studies seeking to assess risk for livestock-to-human transfer of antibiotic resistance and to identify mechanisms for reducing that risk where possible. This study evaluated the impact of forage concentration and supplemental essential oil in beef cattle finishing diets on antibiotic resistance in freshly excreted and consolidated beef feedlot manure. Results indicate that antibiotic resistance in manure was not impacted by either of the two dietary treatments considered. Continue reading “Dietary Impact on Antibiotic Resistance in Feedlot Manure”

Antibiotic Resistance in Manure-Amended Agricultural Soils

Report on research conducted at the University of Nebraska, originally printed in the 2021 Nebraska Beef Cattle Report.

Summary with Implications  

Manure application to agricultural land benefits soil health and agronomic yields. However, as antibiotic resistance becomes a more serious threat to public health, there is concern that antibiotic resistance originating from livestock manure could impact human health through contamination of the environment or food. This study sought to quantify this risk by monitoring concentrations of antibiotic-resistant bacteria and genes in fallow soil during the period of October through April, representing fall manure application through spring planting. Resistance to three common antibiotics – tylosin, azithromycin, and tetracycline – was monitored following application of fresh, stockpiled, or composted beef feedlot manure, or inorganic fertilizer. Overall, concentrations of all monitored resistant bacteria were below the detection limit for enumeration. Results indicate that while all the manure treatments increased at least one measure of antibiotic resistance during the sampling period, by the final sampling day antibiotic resistance prevalence and concentrations in manured plots were not significantly different from soil receiving no fertilizer treatments  Continue reading “Antibiotic Resistance in Manure-Amended Agricultural Soils”

Antibiotic use in food animals and its effect on antimicrobial resistance spread and human health

Most people alive today have never known a world without antibiotics. Antibiotics became widely used to treat bacterial infections in the 1930s and ‘40s, and were quickly labeled a “miracle drug”. But, as the widespread use of antibiotics evolved, so did the discovery of antibiotic-resistant bacteria. And we have now entered an era where antibiotic resistance is considered one of the biggest worldwide public health challenges of our time.

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We can learn a lot from poop

A summary of Using sewage for surveillance of antimicrobial resistance by Aarestrup and Woolhouse (2020)

Key Points

  • Sewage-based surveillance for antimicrobial resistance provides a flexible, scalable, and quickly implementable AMR tracking method.
  • Advances in DNA sequencing enable faster and more responsive resistance monitoring, which is essential to address AMR surveillance worldwide.

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Antimicrobial Resistant Bacteria in Surface Water Bodies

Antimicrobial resistance is a challenge that many face today in the agricultural field. As antibiotics and supplements are given to farm animals and their manure applied to crops and pasture, microbes are demonstrating resistance to antibiotics in agricultural settings. These bacteria have also been found residing in surface water bodies after being influenced by agriculture or animal production. These highly resistant bacteria have caused problems for human health with exposure to these bacteria.

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The growth of antibiotic resistance has become a serious threat to human health

A brief summary of the manuscript, Update on the Antibiotic Crisis by Rossolini et al. (2014)

Key Points:

  • Developing new antibiotics is only a stop-gap solution to a growing antibiotic resistance crisis.
  • Drugs able to treat the newest strains of resistant bacteria are still years away, while resistance continues to spread.

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Composting can reduce antimicrobial resistance in manure

A brief summary of the manuscript, Dissipation of Antimicrobial Resistance Determinants in Composted and Stockpiled Beef Cattle Manure by Xu et al. (2016)

Key Points:

  • Composting manure can reduce pathogen presence and antimicrobial residues in manure.
  • Composting efficacy in reducing antimicrobial residues in manure is associated with elevated temperatures within the composting process.
  • Stockpiling manure marginally reduce pathogen presence and antimicrobial residues in manure when compared to composting.

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Application of organic fertilizers increases antibiotics in soil

A brief summary of the manuscript, Use of commercial organic fertilizer increases the abundance of antibiotic resistance genes and antibiotics in soil by Zhou et al. (2016)

Key Points:

  • Residual antibiotics can persist in soil for months following the application of manure-based, commercial organic fertilizers.
  • Antimicrobial resistance and antibiotic residues decreased significantly over the first 60 days following fertilizer application but did not return to background levels until four months after application.

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Antibiotic resistance higher in environments impacted by human or animal waste.

A brief summary of the manuscript, Antimicrobial-resistant bacterial populations and antimicrobial resistance genes obtained from environments impacted by livestock and municipal waste (Agga et al., 2015)

Key Points

  • Antibiotic resistance is naturally occurring in almost any environment, making it difficult to determine what is the true human health risk associated with any change in environmental bacterial populations or genes.
  • This study found higher concentrations of resistant bacteria in both treated municipal wastewater and livestock wastes than are naturally present in soil or water.
  • Municipal wastewater samples contained a wider variety of antibiotic-resistant genes than were present in livestock wastes.

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An array of veterinary antibiotics has been found in water and soil samples

A brief summary of the manuscript, Summary of veterinary antibiotics in the aquatic and terrestrial environment (Kemper, 2008), a review of studies looking at the presence of clinical antibiotics in the native environment.

Key Points

  • All antibiotics used by people or animals contribute to the development of antimicrobial resistance (AMR).
  • Antibiotics used in livestock production have the potential to contribute to increasing pools of antibiotics in soil due to manure application or deposition.
  • The biggest contributor to antibiotics in the surface water is a likely municipal (human) waste.

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