|Kasumba, John - Western Kentucky University|
|Appala, Keerthi - Western Kentucky University|
|Conte, Eric - Western Kentucky University|
Submitted to: Proceedings of Pittcon Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 10/16/2018
Publication Date: 3/19/2019
Citation: Kasumba, J., Appala, K., Agga, G.E., Loughrin, J.H., Conte, E.D. 2019. Anaerobic degradation of tetracycline antibiotics in agricultural manure. Proceedings of Pittcon Meeting. Poster No. 890-2P.
Technical Abstract: Each year, vast amounts of tetracycline antibiotics are used globally in agriculture for the treatment of diseases and the promotion of livestock growth. However, most of these antibiotics are excreted into the environment by livestock either unaltered or as metabolites, resulting in a potential public health hazard, primarily through the development and spread of antibiotic-resistant bacteria. Anaerobic digestion is one of the most common methods used to reduce the concentrations of antibiotics in the manure before it is applied on agricultural fields. In this study, tetracycline antibiotics (tetracycline [TC], oxytetracycline [OTC] and chlortetracycline, [CTC]) were spiked in swine, cattle, and poultry manure that was diluted with distilled water. The diluted manure was anaerobically digested inside air-tight laboratory-made PVC batch reactors for 64 days at room temperature. Samples of the digested manure were taken every 8 days and analyzed for tetracyclines and their main metabolites using LC-MS/MS. The degradation rate constants and half-lives of the parent tetracyclines were determined following first-order kinetics. The concentrations of the tetracyclines reduced in the ranges of 4 - 73%, 26 - 72%, and 69 - 88% for TC, OTC, and CTC, respectively, in all the three manure types studied. The highest degradation rate of CTC was observed in swine manure (k = 0.0161 ± 0.0026 d-1) corresponding to a half-life of 43.0 days, while its lowest degradation rate was observed in poultry waste (k = 0.0043 ± 0.0036 d-1; half-life = 161.0 days). The half-lives for OTC ranged between 89.3 and 141.0 days, while TC exhibited the longest persistence of all the tetracycline antibiotics studied with half-lives ranging from 92.6 days to 340.1 days. In general, the tetracyclines were found to degrade faster in cattle manure compared to swine and poultry manure. The results of this study demonstrate that tetracycline antibiotics are persistent in manure after anaerobic digestion, which can thus contribute to the spreading of antibiotic resistance in the environment.