SETAC Globe - Environmental Quality Through Science
19 February 2015
Volume 16 Issue 2
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Antibiotics in Agroecosystems: State of the Science “AROSOS” Workshop Summary

Jean E. McLain, University of Arizona Water Resources Research Center, Daniel Snow, University of Nebraska Water Sciences Laboratory, Lisa Durso, USDA-ARS Agroecosystem Management Research Unit, J. Brett Sallach, University of Nebraska-Lincoln Civil Engineering

Agroecosystems

In August 2014, the Biosphere2 Conference Center in Oracle, Arizona was the site of a sunny, three-day workshop on “Antibiotics in Agroecosystems: State of the Science.”

The meeting was attended by 42 scientists and others from academia, government agencies (including USEPA and USDA), and industry. Approximately one-third of the registrants were students, and nearly 20 percent represented international organizations. Nine of the attendees were SETAC members, including a co-organizer and one of the four experts invited to speak about specific challenges of antibiotics and antibiotic resistance in agricultural ecosystems. The event was funded through a grant from the USDA Agricultural and Food Research Initiative, Food Safety Challenge Area, which specifically supports research and activities that will develop outcomes for decisions and policies to contribute to a safe food supply and the reduction of foodborne disease.

Over the past two decades, there has been extensive research on the correlation between the use of antimicrobials and the development of antibiotic resistance (AR) in clinically relevant human and foodborne pathogens. Workshop organizers and attendees first agreed that, in order to facilitate the goal of reducing the transfer of AR from agroecosystems to human clinical settings, it is essential to better understand the natural levels and the fate and transport of specific types of AR. Currently, there is no consensus on which antibiotics, which types of resistance, or which specific AR genes are most relevant to the scientific study of how agricultural antibiotic use impacts human health.

In light of the urgent need expressed by the World Health Organization for “internationally recognized principles for risk assessment … related to antimicrobial resistance owing to non-human use of antimicrobials” (WHO 2009), there are yet unaddressed issues among the research community involved in environmental tracking of antibiotics, AR bacteria and AR genes. One solution would be to develop a set of more standardized and rigorously validated methods that can be used across the farm-to-fork continuum to inform food safety risk assessment models. This critical, as yet completely un-addressed need, provided justification for the ARASOS workshop at Biosphere2.

Four international experts were invited to speak: Alistair Boxall with the University of York, UK, addressed the risks of antibiotics in the environment. Diana Aga with the University of Buffalo, The State University of New York, USA, talked about the challenges in detection of antibiotics in soil and water, followed by Amy Pruden with Virginia Tech University, USA, who presented molecular methods for detection of AR genes in environmental samples. And Eddie Cytryn with the Agricultural Research Organization, Volcani Center, Israel, addressed confounding effects of natural, background levels of AR in the environment.

The four invited presentations provided a framework for discussing the accurate detection and assessment of the potential effects of antibiotics and AR in the environment, and the talks were designed to stimulate constructive interdisciplinary dialogue on how to best measure AR in soil and water.

Following the introductory “State of the Science” presentations, workshop attendees divided into three breakout groups to identify specific research questions

Key questions and conclusions from each breakout group were reported to the collective and are shown below.

Breakout Group 1: Challenges and methods of measuring background and natural levels of resistance in the environment
How do we establish baseline measurements in order to assess efficacy of proposed interventions and how can these requirements be worked into study design? What methods should be used to assess background and natural levels of resistance? It was agreed that definitions for data collection and standards for reporting must be established.

Breakout Group 2: Current methods for examination of trace antibiotics in natural (soil, water) environments
What criteria should be used by researchers to decide which drugs will provide the most useful information for issues concerning impact of veterinary antibiotic use on human health? How does measurement of antibiotic metabolites and transformation products fit into studies focused on antibiotic resistance in agroecosystems? The development of standards for publishing of antibiotic data is necessary, similar to the EU Manure Testing Guideline that specifically identifies list of substrate characteristics that need to be reported in addition to the antibiotic concentrations.

Breakout Group 3: Molecular and cultural methods for tracking AR bacteria and AR genes in environmental samples
Are some types of resistance a higher priority than others? Should the research community consider standard methods, similar to USEPA standards for water quality monitoring? Should the community consider standard quality data reporting requirements? The need for experiments that focus on the link between AR genes and human health risks is of critical importance.

Cross-disciplinary discussions helped identify several challenges to research on antibiotics and AR in the environment. These challenges included:

  1. A need for funding to measure the occurrence and effects of antibiotics in agroecosystems and linking this to human health effects
  2. Experimental design to determine bioavailability or bioactivity and effects of non-extractable residues and degradation products
  3. Are there synergistic effects of mixtures over individual antibiotics in the environment?
  4. How can actual environmental risks be communicated to the public? 

The use of antibiotics in food production has tremendous environmental and ecological benefits, but linking antibiotic use, occurrence and development of resistant bacteria is a major challenge. Public health risk assessment must include agreement on proper methods for environmental detection of antibiotics, AR bacteria and genes, so all three can be addressed simultaneously.

ARASOS workshop attendees resolved to share this message through a series of five “State of the Science” manuscripts, which will be submitted to a peer-reviewed journal  in 2015. The five papers, led by teams of researchers and graduate students, will cover:

  1. Antibiotics in Agroecosystems: State of the Science
  2. Issues in Detection of Antibiotics and their Significance in the Environment
  3. Background Antibiotic Resistance and Frameworks for Research
  4. Molecular Methods and Gaps in Knowledge
  5. Cultural Methods and Gaps in Knowledge

Together, these papers will provide a framework of the best available methods for measuring antibiotics and antibiotic resistance in agroecosystems, and they will propose guidelines for validation of AR research. In addition to the five review papers, we invite original articles that address high-quality research involving antibiotic and AR detection in environmental samples. More information on participating in the special issue please contact Daniel Snow prior to 26 February.

References
World Health Organization (WHO). 2009. Critically important antimicrobials for human medicine, 2nd revision.

Author's contact information: dsnow1@unl.edu

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