|Chee Sanford, Joanne|
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 1/1/2012
Publication Date: 3/14/2012
Citation: Chee Sanford, J.C., Krapac, I.J., Yannarell, A.C., Mackie, R.I. 2012. Environmental impacts of antibiotic use in the animal production industry. In: Norrgren, L., Levengood, J., editors. Ecosystem Health and Sustainable Agriculture. Book 2. Uppsala, Sweden: The Baltic University Programme. p. 228-368. Interpretive Summary: The widespread use of antibiotics in agriculture has raised concerns over the increasing emergence of antibiotic resistances in bacteria and whether the genes conferring resistances can be widely disseminated in the environment. The molecular ecology of antibiotic resistance genes in the environment is poorly understood, particularly in regards to the occurrence of these genes in soil and water with and without impact from animal waste. Agricultural soils with known histories of manure addition have the consquence of receiving known inputs of bacteria and their corresponding resistance genes along with high carbon and nitrogen loads, sets up opportunity for enhanced transfer of genetic material between microbial populations. Such exchange of genes has longer-term ecological impact on microbial function in general, leading to longer term effects on soil and plant health. The significance of this report summarizes our knowledge of the occurrence and persistence of genetic transfer among natural soil microbial populations and improves our understanding of the impact of agricultural practices on the environment.
Technical Abstract: Antibiotics are routinely used in the livestock industry to treat and prevent disease. At subtherapeutic concentrations, antibiotics can select for resistant bacteria in the gastrointestinal tract of production animals, providing a potential reservoir for dissemination of drug resistant bacteria into other animals, humans and the environment. Bacteria have been shown to readily exchange genetic information in nature, permitting the transfer of different resistance mechanisms already present in the environment from one bacterium to another. Such genetic transfer has been hypothesized to occur in part due to selective pressures but acquisition of resistance traits may also be associated with intrinsic modifications to genes involved in housekeeping functions unrelated specifically to antibiotics themselves. Because native populations are generally better adapted for survival in aquatic or terrestrial ecosystems, persistence of resistance traits may be likely in natural environments once they are acquired. Antibiotic resistance has received considerable attention due to the problem of emergence and rapid expansion of antibiotic resistant pathogenic bacteria. The potential for long-term, cumulative inputs of antibiotics and correspondingly, their potential effects on acquisition and maintenance of antibiotic resistance mechanisms as well as other ecologically significant functions in bacteria, collectively suggest a degree of impact on the occurrence, persistence, and mobility of resistance genes in natural environments. In the following review, we provide an overview of antibiotic use and animal waste management in the United States, the dissemination and fate of antibiotic residues, and the environmental persistence, mobility, and transferability of antibiotic resistance determinants and their bacterial hosts in the context of environmental conditions encountered during the course of manure storage and in natural soil and water environments following the practice of land application of animal waste. This description provides a background to determining the true ecological impact of antibiotics and antibiotic resistance genes in natural environments.