Abstract
The widespread occurrence of antibiotics in the environment may exert a negative impact on wild organisms. In addition, they can become environmental reservoirs, through the ingestion of food or contaminated water, and vectors for antibiotic-resistant bacteria. This fact is even more important in migratory birds that can promote their dissemination across continents. In this work, a multiresidue analytical method suitable for the determination of five families of antibiotics and their main metabolites in waterbird faeces has been developed and validated. The target compounds include environmentally significant sulfonamides, macrolides, fluoroquinolones, tetracyclines and antifolates. Sample treatment involves ultrasound-assisted extraction with methanol and dispersive solid-phase extraction clean-up with C18. Analytical determination was carried out by liquid chromatography–tandem mass spectrometry. The most significant parameters affecting sample extraction and extract clean-up were optimised by means of experimental designs. Good linearity (R2 > 0.994), accuracy (from 41 to 127%), precision (relative standard deviation lower than 24%) and limits of quantification (lower than 2 ng g−1 (dry weight, dw)) were obtained for most of the compounds. The method was applied to the determination of the selected compounds in 27 faeces samples from three common migratory waterbird species. Nine antibiotics and three of their metabolites were detected in the analysed samples. Fluoroquinolones and macrolides were the antibiotics most frequently detected. The highest concentrations corresponded to norfloxacin (up to 199 ng g−1 dw).Graphical abstract
Highlights
The widespread use of antibiotics in human and veterinary medicine may lead to their environmental dissemination through discharges from wastewater treatment plants (WWTPs), animal farms and aquaculture ponds [1]
LC–MS/MS parameters were optimised by injection of individual and mixture standard solutions of the selected compounds at 1 mg L −1
The highest intensities were provided by ammonium formate 10 mM containing 0.05% v/v of formic acid so that mixture was selected as aqueous mobile phase solvent
Summary
The widespread use of antibiotics in human and veterinary medicine may lead to their environmental dissemination through discharges from wastewater treatment plants (WWTPs), animal farms and aquaculture ponds [1]. Analytical methods reported to date for the determination of pharmaceuticals in animal excrements have been focused on bovine manure [21,22,23], swine manure [21,22,23,24,25,26,27,28] and poultry excreta [2, 29, 30] The aim of such studies is to evaluate the presence of veterinary antibiotics in manure or excreta because they can constitute a significant route of antibiotic dissemination into the environment and because they could enter in the human food chain when manure is used in crops as low-cost organic fertilisers. Because of all the mentioned above, it is necessary to develop analytical methods for the specific determination of antibiotics and their metabolites in wild bird faeces as they constitute promising to non-invasive and easy to collect matrix to monitor exposure to antibiotics
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