In Norway, the use of quinolones in livestock populations is very low, and prophylactic use is prohibited. Despite this, quinolone resistant E. coli (QREC) are present at low levels in several animal species. The source of these QREC is unknown. The aim of this study was to characterize and compare QREC from different animal species to identify putative factors that may promote the occurrence of QREC. A total of 280 QREC isolates, from broilers, pigs, red foxes and wild birds, were whole genome sequenced and analysed. Well-known chromosomal and plasmid-mediated resistance mechanisms were identified. In addition, mutations in marR, marA and rpoB causing novel amino acid substitutions in their respective proteins were detected. Phylogenetic analyses were used to determine the relationships between the isolates. Quinolone resistance mechanism patterns appeared to follow sequence type groups. Similar QREC isolates with similar resistance mechanism patterns were detected from the samples, and further phylogenetic analysis indicated close evolutionary relationships between specific isolates from different sources. This suggests dissemination of highly similar QREC isolates between animal species, and also persistence of QREC strains within the broiler production chain. This highlights the importance of both control measures at the top of the production chain, as well as biosecurity measures to avoid further dissemination and persistence of QREC in these environments.

Significance of study Since antimicrobial usage is low in Norwegian animal husbandry, Norway is an ideal country to study antimicrobial resistance in the absence of selective pressure from antimicrobial usage. In particular, the usage of quinolones is very low, which makes it possible to investigate the spread and development of quinolone resistance in natural environments. Comparing quinolone resistant E. coli (QREC) from livestock and wild animals in light of this low quinolone usage provides new insights into the development and dissemination of QREC in both natural- and production environments. With this information, preventive measures may be taken to prevent further dissemination within Norwegian livestock and between other animals, thus maintaining the favourable situation in Norway.

在挪威，喹诺酮类药物在牲畜种群中的使用率非常低，因此禁止预防性使用。尽管如此，在几种动物中，喹诺酮抗性大肠杆菌（QREC）的含量较低。这些QREC的来源未知。这项研究的目的是表征和比较不同动物物种的QREC，以识别可能促进QREC发生的假定因素。对来自肉鸡，猪，赤狐和野生鸟类的总共280个QREC分离物进行了全基因组测序和分析。确定了众所周知的染色体和质粒介导的抗性机制。此外，marR，marA和rpoB中的突变在它们各自的蛋白质中检测到导致新的氨基酸取代的原因。系统发育分析用于确定分离株之间的关系。喹诺酮耐药机制模式似乎遵循序列类型组。从样品中检测到具有相似耐药机制模式的相似QREC分离株，进一步的系统进化分析表明，不同来源的特定分离株之间存在密切的进化关系。这表明在动物物种之间传播高度相似的QREC分离株，以及在肉鸡生产链中QREC菌株的持久性。这凸显了生产链顶端的控制措施以及避免在这些环境中QREC进一步传播和持续存在的生物安全措施的重要性。

研究的意义由于在挪威畜牧业中抗菌药物的使用率较低，因此挪威是研究抗菌素耐药性的理想国家，并且没有来自抗菌药物使用的选择性压力。特别地，喹诺酮类的使用非常少，这使得可以研究在自然环境中喹诺酮抗性的扩散和发展。鉴于喹诺酮的这种低使用量，比较了来自牲畜和野生动物的喹诺酮抗性大肠杆菌（QREC），为在自然和生产环境中QREC的开发和传播提供了新的见识。有了这些信息，就可以采取预防措施，防止在挪威家畜内以及其他动物之间进一步传播，从而保持挪威的有利局势。