Abstract
Simple SummaryOxytetracycline (OTC) is an antibiotic used mainly in feed and drinking water. OTC is poorly absorbed in the gastrointestinal tract of poultry; making droppings a potential route of dissemination of this antibiotic. The aim of this study was to evaluate the dissemination of oxytetracycline excreted from treated birds to the environment and other untreated animals (sentinels), through the analysis of their droppings and litter by HPLC-MS/MS following the end of treatment. In treated bird droppings, the average concentration of OTC+4-epi-OTC ranged from 347.63 to 2244.66 µg kg−1. OTC+4-epi-OTC in litter reached concentrations of 22,741.68 µg kg−1. Traces of OTC+4-epi-OTC were detected in the droppings and litter from sentinels. Therefore, OTC+4-epi-OTC can persist in the litter of treated animals at high concentrations and can be transferred to untreated birds that share the same environment. This exposure has the potential to increase the likelihood of selection of resistant bacteria in the environment. Oxytetracycline (OTC) is widely used in broiler chickens. During and after treatment a fraction of OTC is excreted in its original form and as its epimer, 4-epi-OTC in droppings. To address the transfer of OTC into the environment, we evaluated the dissemination of OTC and 4-epi-OTC from treated birds to the environment and sentinels, through the simultaneous analysis of broiler droppings and litter. Male broiler chickens were bred in controlled conditions. One group was treated by orogastric tube with 80 mg kg−1 of OTC and two groups received no treatment (sentinels). OTC+4-epi-OTC were analyzed and detected by a HPLC-MS/MS post the end of treatment. The highest concentrations of OTC+4-epi-OTC were detected in the droppings of treated birds 14-days following the end of treatment (2244.66 µg kg−1), and one day following the end of treatment in the litter (22,741.68 µg kg−1). Traces of OTC+4-epi-OTC were detected in the sentinels’ droppings and litter (<12.2 µg kg−1). OTC+4-epi-OTC can be transferred from treated birds to the environment and to other untreated birds. The presence and persistence of OTC+4-epi-OTC in litter could contribute to the selection of resistant bacteria in the environment, increasing the potential hazard to public and animal health.
Highlights
Tetracyclines, which were discovered in the 1940s, are broad spectrum bacteriostatic antibiotics [1,2]
The analytical procedure for OTC and 4-epi-OTC detection by HPLC-MS/MS was optimized from work previously published by Berendsen et al [13] with the aim of extracting OTC and its epimer, from droppings and broiler litter
OTC and 4-epi-OTC in droppings and litter from therapeutically treated broiler chickens were detected following the end of treatment
Summary
Tetracyclines, which were discovered in the 1940s, are broad spectrum bacteriostatic antibiotics [1,2] In some countries, such as Brazil and China these antibiotics can be used to promote growth in farm animals. This practice was banned in Europe in 2006 and in the USA in 2017 [3,4]. When OTC is administrated to birds either for treatment or as growth promoter, residues of the antibiotic persist in their products and by-products, and are excreted in droppings [6,8,9,10,11]. Animals can excrete a significant proportion of the administered antibiotics (17–90%) unchanged or as active metabolites (epimers or isomers) of the parent antimicrobial [14]
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