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380 Award Talk: Antimicrobial alternatives in swine and cattle production systems: Do they contribute to or mitigate antimicrobial resistance?

Year: 2025
Type: conference-abstract
Abstract: Antimicrobial agents are widely employed in swine and cattle production systems to treat and prevent diseases. The overall benefits include increased animal productivity, improved animal health, and reduction in gut prevalence and fecal shedding of foodborne pathogens such as Shiga-toxin producing Escherichia coli, Salmonella and Campylobacter. The use of in-feed antimicrobials is of concern because of the emergence and dissemination of antimicrobial resistance (AMR) bacteria within the gut microbial ecosystem. These resistant bacteria, or the genetic elements they carry, can be transmitted to humans through the food chain, direct animal contact, or environmental pathways, ultimately posing a threat to public health by limiting treatment options for bacterial infections. The emergence and persistence of AMR in food-producing animals are driven by a complex interplay of microbial, host, and environmental factors. This complexity highlights the urgent need to better understand the ecological and evolutionary consequences of antimicrobial use particularly its impact on microbial community structure, resistance gene reservoirs, and the horizontal gene transfer dynamics within the gastrointestinal tract. Insights into these processes are critical for developing effective strategies to limit the spread of resistance without compromising animal health or productivity. A potential approach to AMR mitigation is to minimize or eliminate exposure of gut bacteria to antimicrobials by minimizing oral administration of antimicrobials. This approach aligns with global efforts to implement antimicrobial stewardship practices in animal agriculture and encourages the exploration of alternative interventions that can maintain animal performance while mitigating the selection pressure for resistance. Because of public health concern associated with AMR, antimicrobial alternatives, such as heavy metals, mainly copper and zinc, probiotics and essential oils, are being used to achieve health and performance benefits similar to antimicrobials. The alternatives are sustainable because performance benefits are attained with a concurrent reduction in the overall antimicrobial use. Additionally, the changes in the gut microbial community composition induced by antimicrobial alternatives could have favorable effects in mitigating AMR in gut bacteria. However, antimicrobial alternatives, particularly copper, zinc and certain probiotics, have the potential to contribute to AMR in gut bacteria. Copper and zinc, particularly at elevated levels in the feed, induce metal resistance in bacteria and genes that confer metal resistance have been shown to be genetically linked to other AMR genes, suggesting potential co-selection of AMR in the absence of antibiotic selection pressure. Similarly, probiotics, particularly Enterococcus faecium, which is one of the commonly used probiotic species, can carry virulence genes and AMR genes to medically-important antibiotics and have the potential to horizontally transfer the genes to other bacteria, including pathogens in the gut. In conclusion, antimicrobial alternatives used in livestock production must be critically evaluated not only for their benefits but also for their potential to contribute to AMR. Any intervention that alters the microbial community has the potential to select for resistance. Therefore, coordinated, interdisciplinary efforts involving human and animal health sectors are essential to guide research and ensure the safe and effective use of antibiotic alternatives in food animal production systems.
DOI: 10.1093/jas/skaf300.057
Language: English
Open Access status: bronze
OpenAlex ID: W4414830612
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