|Chee Sanford, Joanne|
Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/20/2008
Publication Date: 5/1/2009
Citation: Chee Sanford, J.C., Mackie, R.I., Koike, S., Krapac, I., Maxwell, S., Lin, Y., Aminov, R.I. 2009. Fate and Transport of Antibiotic Residues and Antibiotic Resistance Genetic Determinants During Manure Storage, Treatment, and Land Application. Journal of Environmental Quality. 38(3):1086-1108. Interpretive Summary: Antibiotics are used in swine production at high concentrations to treat disease and at sub-therapeutic levels for growth promotion and improvement of feed efficiency. Most antibiotics are excreted in waste, but exposure in the animal intestinal tract results in selection of antibiotic resistant bacteria, which are also excreted into waste holding environments. One common method of animal waste disposal in the United States is through land application, resulting in environmental entry of antibiotics, bacteria, and resistance genes. There is little knowledge of the effects of environmental concentrations of antibiotics on natural soil microorganisms, and antibiotic resistance genes can persist in both viable and dead cells, allowing opportunity for transfer of the resistance traits among different bacteria. Measurements of antibiotic resistance genes, including quantities, types, and frequencies are still needed. This review article discusses the issues and latest scientific findings concerning the fate, transport, and persistence of antibiotics and antibiotic resistance genes in natural environments, with emphasis on tracking these elements from manure storage, treatment, and land application processes. This article is significant as the first to review research findings obtained in recent years, and provides insight into future research required to understand the impact of antibiotic residues and resistance genes in natural soil and water environments.
Technical Abstract: Antibiotics are used in swine production for therapeutic treatment of disease and at sub-therapeutic levels for growth promotion and improvement of feed efficiency. It is estimated that ca.75% of antibiotics are not absorbed by animals and are excreted in waste. Antibiotic resistance selection occurs in many intestinal bacteria, which are excreted along with their corresponding genetic resistance determinants into waste holding environments. One common method of animal waste disposal in the United States is through land application, resulting in environmental entry of both antibiotics and genetic resistance determinants. Knowledge of the biological activity and environmentally relevant concentrations of antibiotics and their break-down metabolites is important for inferences of impact. There is limited field information on the biological activity of residues, and their fate and transport. Survival of fecal bacteria can range from 8 weeks to 6 months, but vary depending on species and temperature. Genetic elements can persist in both viable and dead cells, however, the spatiotemporal dynamics of microbial populations and the potential for gene transfer are not well understood. Quantitative measurements of antibiotic resistance genes are needed, in addition to assessment of diversity and frequency. Phylogenetic analysis indicates that antibiotic resistance genes have evolved, although some genes have been maintained in bacteria prior to the modern antibiotic era. Many resistance genes are exchanged among a broad range of bacteria. In order to obtain key data on gene flow, higher throughput and more sequencing of antibiotic resistance genes both from known organisms and the metagenome of different environments is essential. This review article discusses the issues and latest scientific findings concerning the fate, transport, and persistence of antibiotics and antibiotic resistance genes in natural environments, with emphasis on tetracycline and erythromycin as models. The emphasis is on tracking these elements from manure storage and treatment, to soil application.