Oxytetracycline and Monensin Uptake by Tifton 85 Bermudagrass from Dairy Manure-Applied Soil

Sheldon S Hilaire,Jeff A Brady,Barbara Bellows,James P Muir

doi:10.3390/agronomy10040468

Abstract

To address concerns regarding the potential impact of antibiotic use in animal husbandry on antibiotic resistance in humans, we conducted a greenhouse-based study examining uptake of the veterinary antibiotics oxytetracycline (OTC) and monensin (MON) by Tifton 85 Bermudagrass (T85), the most commonly grown forage grass in the southeastern U.S.A. Since oxytetracycline is used in both veterinary and human medicine, its accumulation in animal products could impact human resistance to this antibiotic. Monensin is not used in human medicine but has a high potential for accumulating in the environment. Our research examined antibiotic uptake by forage grass T85, the effect of dairy manure application on its uptake, and antibiotic retention in soil. We compared unspiked, wet dairy manure to wet dairy manure spiked with MON or OTC that was soil surface applied to pots or incorporated into soil. After 6 wk, plant stem/leaf and root tissue, as well as soil samples, were assessed for antibiotic residues using enzyme-linked immunosorbent assay (ELISA). Results confirmed Tifton 85 MON and OTC uptake. Six weeks after adding the antibiotics, the greatest plant matter OTC and MON contents were 157.9 ± 70.6 and 234.4 ± 19.6 µg kg−1, respectively, and 17.6 and 369.5 µg kg−1, respectively, for soil. When spiked with OTC, manure incorporation led to decreased OTC uptake by T85 tissue. Bioaccumulation of these antimicrobials in livestock and in the environment is a potential concern for animal, environmental, and human health.

Highlights

Antimicrobial use in animal production is a major contributor to the increase in antibiotic resistance [1]
Classes of antimicrobials used in cattle production include polypeptides, tetracyclines, macrolides, ionophores and sulfonamides [2]—almost all have some importance in human medicine, except for monensin (MON)
Of the 15,576,975 kg of various classes of antibiotics sold for domestic livestock use in 2015 [5], the ionophore class, including MON, accounted for 30%, while tetracycline accounted for 44% of sales

Summary

Introduction

Antimicrobial use in animal production is a major contributor to the increase in antibiotic resistance [1]. Classes of antimicrobials used in cattle production include polypeptides, tetracyclines, macrolides, ionophores and sulfonamides [2]—almost all have some importance in human medicine, except for monensin (MON). It is not nor expected to be in the future, of importance to human medicine. Of the 15,576,975 kg of various classes of antibiotics sold for domestic livestock use in 2015 [5], the ionophore class, including MON, accounted for 30%, while tetracycline accounted for 44% of sales

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Results

Conclusion