Groupwise antibiotic treatments are common in broiler chicken production. They induce selection for antibiotic resistance in commensal Escherichia coli. This study aimed to investigate antibiotic resistance after individual (I, drenching) or groupwise treatment (G, by water) with amoxicillin, and after contact with I or G (KI or KG), compared with untreated broilers without contact with treated broilers (C), and pretreatment values. Finally, we compared antibiotic resistance from broilers (G) after a second treatment, with a treatment in the contact animals (KG), and a first treatment in the control animals (C). Resistance to ampicillin and other antibiotics was significantly increased in groups G and I within 2 days, suggesting (co-)selection of resistance. The increase was lower in groups KI, KG, and C during the first treatment (days 1–5). The increased resistance in group C was interpreted as a change in the microbiota after initial moving and first feeding. After treatment, resistance rates decreased to initial or lower values in all groups. During the second treatment period (days 34–38), all three groups' (G, KG, and C) resistance levels increased to equally high levels. Cephalosporin resistance was low, and did not change over the experimental period. On days 3 and 38, resistance rates of E. coli from duodenum, jejunum, and cecum did not differ between segments and treatment routes. Overall, the baseline levels of antibiotic resistance in E. coli were high. Amoxicillin triggered an increase in resistance levels, irrespective of the mode of treatment. Substantial resistance dynamics in untreated controls warrant further investigation.

中文翻译：

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实验环境中阿莫西林处理后肉鸡大肠杆菌中的抗生素耐药性。

分组抗生素治疗在肉鸡生产中很常见。它们诱导共生大肠杆菌中抗生素耐药性的选择。这项研究旨在调查与未经处理的肉鸡未接触的未经处理的肉鸡相比，对阿莫西林进行单独（I，淋湿）或逐组处理（G，用水）以及与I或G（KI或KG）接触后的抗生素耐药性）和预处理值。最后，我们比较了第二次治疗后肉鸡（G）对接触动物（KG）的治疗和对照动物（C）的对抗生素的抗药性。G和I组在2天内对氨苄青霉素和其他抗生素的耐药性显着增加，表明耐药性的（共）选择。在首次治疗期间（第1-5天），KI，KG和C组的增加较低。C组中增加的抗性被解释为最初移动和首次进食后微生物群的变化。治疗后，所有组的耐药率均降至初始值或更低。在第二个治疗期间（第34-38天），所有三个组（G，KG和C）的抵抗力水平均升高到同样高的水平。头孢菌素耐药性低，并且在实验期间没有变化。在第3天和第38天，耐药率为十二指肠，空肠和盲肠的大肠杆菌在区段和治疗途径之间没有差异。总体而言，大肠杆菌中的抗生素耐药性基线水平很高。不论治疗方式如何，阿莫西林都会引起耐药性水平的提高。未经处理的对照中的大量耐药性动态值得进一步研究。