ARS | Publication request: Degradation kinetics and mechanism of antibiotic ceftiofur in recycled water derived from beef farm

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 24, 2011
Publication Date: August 24, 2011
Citation: Li, X., Zheng, W., Machesky, M.L., Yates, S.R., Katterhenry, M. 2011. Degradation kinetics and mechanism of antibiotic ceftiofur in recycled water derived from beef farm. Journal of Agricultural and Food Chemistry. 59:10176-10181.

Interpretive Summary: The occurrence of antibiotics in the environment is receiving considerable attention since many of these compounds have the potential to adversely affect human and environmental health. Risks posed by residual antibiotics and their metabolites in the surface and groundwater are receiving considerable attention due to the potential for microorganisms to develop increased antibiotic resistance. Antibiotic resistant genes may be transferred through drinking water and food chains; therefore, it is important to understand the fate and movement of antibiotic residues in water and waste disposal systems, and to develop improved waste handling processes that minimize the loading of antibiotics and their metabolites to the environment. Ceftiofur is an antibiotic that used for the treatment of respiratory diseases in animals and the two primary transformation mechanisms are biodegradation and chemical hydrolysis. The objective of this study was to investigate degradation kinetics and mechanisms for cefitiofur in the recycled water derived from a beef farm and to evaluate the effects of incubation conditions on the degradation rate. This information will increase our understanding of the types and amounts of antibiotics that occur in animal waste and the potential contribution as a source of these compounds to the environment. This study provides important information that will help scientists, regulators and land-use manages to understand the various factors affecting antibiotics in surface and ground water.

Technical Abstract: Ceftiofur is a third-generation cephalosporin antibiotic that has been widely used to treat bacterial infections in concentrated animal feeding operations (CAFOs). Land application of CAFO waste may lead to the loading of ceftiofur residues and its metabolites to the environment. To mitigate the potential contamination of the antibiotic in the environment, the degradation kinetics and mechanisms of ceftiofur in solutions blended with and without the recycled water derived from a beef farm were investigated. In this study, the degradation of ceftiofur in aqueous solutions in the presence of the CAFO recycled water was a combined process of two concurrent transformations: hydrolysis and biodegradation. The total degradation rates of ceftiofur at 15 oC, 25 oC, 35 oC, and 45 oC varied from 0.4-2.8 × 10-3, 1.4-4.4 × 10-3, 6.3-11 × 10-3, and 11-17 × 10-3 h-1 in aqueous solutions blended with 1~5% the CAFO recycled water. For the hydrolysis, the degradation rates of ceftiofur increased as the incubation temperature elevated from 15 to 45 oC. The biodegradation rates of ceftiofur were temperature-dependent and increased with increasing the application rates of the recycled water derived from beef farm. Cef-aldehyde and DCF as main biodegradation and hydrolysis products were identified, respectively, which suggests the primary biodegradation mechanism of ceftiofur was the cleavage of its B-lactam ring while the hydrolytic cleavage occurred in its thioester bond. Unlike DCF and ceftiofur, cef-aldehyde does not contain B-lactam ring and has less antimicrobial activity, indicating that the biodegradation of ceftiofur in the animal wastewater may mitigate the potentially adverse impact of the antibiotic to the environment.