A Systematic And Integrated Approach To Mitigation Of Antimicrobial Resistance In Aquaculture

The long-term goal of our team is to ensure and promote the sustainable growth and development of U.S. aquaculture by supporting the scientific and prudent use of antimicrobials without the unintended consequence of AMR development. The main goal of this application is to identify critical control points and mitigation strategies for preventing the development of antimicrobial resistance (AMR) bacteria and the horizontal transfer of antimicrobial resistance genes (ARGs) in aquaculture production systems. To achieve this goal, our experienced team will use an integrated approach to pursue the following specific objectives:Examine AMR development in catfish when aquaculture antibiotics are applied at different water temperatures using a model aquaculture system. Occurrence of the most economically important bacterial diseases in catfish is temperature dependent. Each pathogen has its preferred break-out temperature. When an outbreak occurs, a bacterial etiology is suspected, an antibiotic is prescribed provided no resistance to this antibiotic is identified from the outbreak isolate. Antibiotics used in the U.S. aquaculture are broad-spectrum, and each can be used for controlling different bacterial infections. For example, Aquaflor® and Romet® can both be used to treat enteric septicemia of catfish caused by E. ictaluri, and Terramycin® and Romet® can both be used for treating Aeromonas infections. The treatment efficacy of these drugs has been tested and proven at different water temperatures, and they have been used interchangeably for different fish infections. However, since it is also known that the half-life of antibiotics in water is influenced by water temperatures, a critical knowledge gap has become apparent regarding the use of various antibiotics in aquaculture at different temperatures and their impacts on AMR development. A key question that needs to be addressed is, as these antibiotics are efficient for controlling fish infections at a wide range of water temperatures and are used interchangeably for certain fish infections, but their half-life in water is impacted by water temperatures, are their impacts on AMR formation the same or different? The first objective of this proposal aims to answer this question and close the above knowledge gap by applying different antibiotics to a model catfish system at different water temperatures relevant to natural disease outbreaks. To ensure the results will be applicable and useful for all U.S. aquaculture farmers, two types of water sources will be used. U.S. aquaculture farmers use two main water sources for charging and recharging their ponds. While farmers in the southern U.S. have access to generous quantities of surface water, aquaculture farmers in regions like southern California rely on well water to charge their ponds. We hypothesize that the impact of antibiotics used in aquaculture on the development of AMR varies at different water temperatures and that the interaction between temperature and AMR formation may also be influenced by the water source. To test this hypothesis, channel catfish (Ictalurus punctatus), the leading catfish species farmed in the U.S., will be used as the model fish species. A treatment study in a well water system will be conducted at UC Davis, with another treatment study in a surface water system conducted at Auburn University. Three aquaculture antibiotics (Terramycin®, Romet® and Aquaflor®) will be applied to the model systems separately, and their impact on AMR formation will be examined at three different water temperatures (20°, 25°, and 30° C). Once completed, the study will yield a guideline for appropriate use of antibiotics that mitigates AMR development in aquaculture production.Determine the impact of antibiotic application at different water temperatures on ARG development and transfer in rearing water. A unique aspect of medication in aquaculture is the unavoidable release of medicated feed directly into the production water pond. How the application of medicated feed affects AMR in water system remains unknown. Answering this question is critical for minimizing the environmental impact of antimicrobials in aquaculture and also for sustaining aquaculture water systems. We hypothesize that different antibiotic-water temperature combinations will have varied impacts on the resistome present in the rearing water. To examine this hypothesis, water samples will be collected from the catfish tanks used for Objective 1. Resistomes present in the rearing water as well as the horizontal transfer of ARGs in the water will be analyzed. Educate aquaculture farmers and veterinarians about appropriate use of antibiotics by developing outreach and education programs using information and guidelines generated from this project. There are three target audiences for our extension and education programming: aquaculture farmers, field veterinarians and the next generation of veterinarians. To achieve this objective, we will enlist the support and involvement of different industrial organizations and extension programs and platforms. For farmers and field veterinarians, results and guidelines generated will be summarized into information brochures using laymen's terms and shared and distributed at face-to-face workshops and by online media, e.g. extension websites, trade association websites, and social media. To educate field veterinarians and next-generation veterinarians, the team will develop three 50-min PowerPoint presentations covering the topics of bacterial infections in fish and treatment strategies; antimicrobial resistance development and mechanisms; and mitigation based on interactions of antibiotics, disease break-out temperatures and water sources. The presentations will be given via a series of webinars and workshops, and will also be incorporated into the teaching curricula at UC Davis School of Veterinary Medicine and Auburn University College of Veterinary Medicine. Learning outcomes and knowledge gains of participating farmers and veterinarians will be evaluated via after-training/workshop surveys and/or in person interviews. The knowledge gain of the next generation veterinarians will be assessed by issuing pre-training and post-training surveys. One unique aspect about our extension and education programming is the involvement of food system institutes. Since AMR is not only about animal health but also food safety, having the Auburn University Food Systems Institute and the Western Institute for Food Safety and Security involved in our Extension programs and being part of our information communication platform, we are able to reach not only producers and veterinarians but also consumers. This will lead to an overall enhanced awareness of AMR in general public.