Developing a multiclass LC-MS/MS method for the analysis of veterinary antimicrobials in water and manure matrices

Authors: CONGILOSI, JENA - University At Buffalo; Moorman, Thomas; IVERSON, ALYSSA - Iowa State University; CRAIG, ANDREW - Iowa State University; ALT, LAURA - Iowa State University; HOWE, ADINA - Iowa State University; SOUPIR, MICHELLE - Iowa State University; AGA, DIANA - Iowa State University

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 8/15/2020
Publication Date: 8/15/2020
Citation: Congilosi, J., Moorman, T.B., Iverson, A., Craig, A., Alt, L., Howe, A., Soupir, M., Aga, D. 2020. Developing a multiclass LC-MS/MS method for the analysis of veterinary antimicrobials in water and manure matrices. In: Proceedings of the American Chemical Society, August 15, 2020, San Francisco, California.

Interpretive Summary:

Technical Abstract: Land application of manure is the most common method of recycling organic matter and nutrients back to cropland in the United States (U.S.) However, swine manure is a hotspot for contaminants such as antimicrobials, antimicrobial resistant bacteria (ARB), antimicrobial resistance genes (ARGs), hormones, and pesticides. Over 15.6 million kilograms of veterinary antimicrobials are sold yearly in the U.S. alone for disease control and growth promotion of livestock. (1) About 90% of administered antimicrobials can pass through the animal unchanged. Antimicrobial residues in manure can be introduced into the environment during manure fertilization and can persist in soil due to insufficient degradation. (2) The widespread use of antimicrobials in animal agriculture has been shown to increase the occurrence of ARB and ARGs in the environment (3) and can therefore impact human health from exposure to contaminated food or water. The STRIPS (Science-based Trials of Rowcrops Integrated with Prairie Strips) team at Iowa State University (ISU) has developed prairie strips systems to border crop fields. (4) These strips are typically composed of native prairie forbs and grasses such as Indiangrass (Sorghastrum Nash), Big Bluestem (Andropogon gerardii), and Little Bluestem (Schizachyrium Nees) Nash). (5) Previous work has demonstrated the benefits of prairie strips systems to soil, water, and biodiversity; while additional studies have reported the efficiency of narrow grass hedges on reducing ARGs in runoff water. Vegetative barriers placed downslope of croplands are able to reduce runoff volume and therefore promote the deposition of sediment-bound contaminants. Moreover, they enhance infiltration and the ability of soil to retain the organic pollutants in runoff water, (6) showing promise for the use of prairie strips as an exciting alternative. This study aims to develop an all-inclusive liquid chromatography tandem mass spectrometry (LC-MS/MS) method for the analysis of 25 veterinary antimicrobials and 2 ß-lactam metabolites. Using this method, concentrations of antimicrobials were evaluated in water and manure matrices to determine the effectiveness of the prairie strips at retaining antimicrobials from manure-amended croplands. Preliminary experiments involved a small-scale laboratory flume study with simulated runoff and were completed at ISU. Samples of manure injected rainwater that was run through prairie grass strips within the flume test section, as well as manure samples used in the experiments, were analyzed for antimicrobials. A previously reported method by Wallace et al. (7) was modified to include additional antimicrobials such as a pleuromutilin, tiamulin, and the ß-lactam metabolites, penilloic acid andamoxicilloic acid, creating an all-inclusive one-shot analysis. Figure 1 shows a sample chromatogram using the newly optimized method, which utilized (A) 0.1% formic acid (FA) aqueous and (B) 0.1% FA in acetonitrile (ACN) mobile phases, a Restek RaptorTM C18 ultra high-pressure liquid chromatography (UHPLC) column, and a flow rate of 0.4mL/min. A 7-min equilibration period was necessary to ensure that the mobile phase composition and pressure had reached starting parameters, with pump delay time in consideration. The detection limits are approximately 0.20ppb and 3.13ppb for tetracyclines and tiamulin respectively. Preliminary results of manure-injected rainwater run through prairie grass integrated within the flume are represented in Figure 2. The detected antimicrobials, were anhydrotetracycline (ATC), chlortetracycline (CTC), epichlortetracycline (ECTC), epitetracycline (ETC), tetracycline (TC) and tiamulin (TIA); which were the same antimicrobials found in solid manure samples. Overall results revealed no significant differences in the concentrations of antimicrobials from the samples collected upstream and downstream o