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.

Summary

For over fifty years, antibiotics have been used in livestock farming to treat and prevent diseases. However, the use of veterinary pharmaceuticals has increasingly become a topic of public debate. Antibiotics are essential therapeutics in animal husbandry to ensure the health and welfare of livestock, but there has been growing concern due to the potential environmental contamination represented by antibiotic use in livestock. Why? Just as in humans, when livestock receive antibiotics, only a portion of the total antibiotic administered is ultimately used to fight infection; the rest is excreted with the animal’s manure and urine. Depending on how livestock manure is collected, treated, and/or utilized, it could introduce antimicrobial-resistant bacteria and/or genes to the environment.

While people often talk about the overuse of antibiotics, it is important to understand that any amount of antibiotics – whether administered to an animal or person, excreted in animal or human waste, or directly introduced to the environment – has the potential to affect the development of antibiotic-resistant bacterial populations. Once antibiotics are excreted in animal manures, they can break down due to environmental factors, such as temperature, sun exposure, moisture, etc. This is why even though there is a known presence of antibiotics in manures that are used for fertilizer, the concentration of antibiotics being spread on fields is not known. Whether manure is deposited directly on the ground by animals or applied to land following some period of storage, the type and conditions of the soil receiving the manure can also impact AMR.

Most early antibiotics were discovered in the soil so it seems logical that antibiotic compounds and resistant organisms can survive, and even thrive, in soil environments. Moreover, because antibiotics naturally occur in soil, antibiotics that are applied in livestock manure or municipal sludge (solids from wastewater treatment) manure or waste can remain stable and active in soil environments. So, when manure or sludge are applied to land as fertilizer, this creates a potential pathway for antibiotics and antibiotic-resistant bacteria to move from livestock manures, commonly used as fertilizers, to the food supply and environment. The accumulation of antibiotics from livestock manures in soil could also pose a risk to contaminating groundwater or surface water supply because most antibiotics are water-soluble and will move easily in water. Therefore, agricultural best management practices that mitigate nutrient or sediment runoff or infiltration from fields can also help keep manure- and soil-borne antibiotics out of surface and g

roundwater. Interestingly, the authors state that many antibiotics found in aquatic environments are likely from human waste products applied to land. Antibiotics in municipal sewage are a result of un-used antibiotics passing through humans. Antibiotics in treated municipal sewage are persistent because modern wastewater treatment systems are not designed to remove these types of compounds.

In 2008, German researcher Nicole Kemper compiled a review of European studies on the presence of veterinary antibiotics in natural environments and a portion of her summary is replicated in the table below. While the level of risk to humans associated with antibiotics in these environments is still unclear, the consequences of a diminished efficacy in important therapeutics for human and animal health are undeniable. An assessment of the presence of antibiotics in potential pathways for human infection is an important first step to better understanding associated risk.

Antibiotic Found in SoilConcentration (ng/kg)Antibiotic Found in WaterConcentration (ng/l)
Clarithromycin0-67,000Lincomycin21,100; 0-730
Lincomycin8,500Clarithromycin0-260
Sulphadiazine1,000Erythromycin0-1,700
Sulphadimidine11,000Roxithromycin0-560
Sulphametazine2,000Tylosin0-50
Trimethoprim500Sulphadiazine4,130
Ciproflozacin6,000-52,000Sulphamethazine240
Tetracycline450,000-900,000; 0-200,000Sulphamethoxazole0-410; 0-480; 0-66
Oxytetracycline305,000Trimethoprim20; 0-200
Chloretetracycline39,000Ciprofloxacin0-405
Norfloxacin0-120; 0-120
Tetracycline400
Oxytetracycline32,000
Chlortetracycline0-690

Ready for a deeper dive?

Learn more about antibiotic contamination of ground and surface water and the associated risk for antibiotic-resistant infections with these great resources:

Authors

Written by Andrea Harris while a student in the Dept. of Biological Systems Engineering, University of Nebraska. Reviewed by: Amy Schmidt, University of Nebraska and Annie Yarbury, University of Maryland.

The scientific research summarized in this article was published as:

Kemper, N. (2008). Veterinary antibiotics in the aquatic and terrestrial environment. Ecological Indicators, 8(1), 1–13. https://doi.org/10.1016/j.ecolind.2007.06.002.

This article presents the author’s interpretation of the published research for a general audience and should not be considered a reflection of the position or opinion of the researchers.