BACKGROUND Optimal treatment and prudent use of antimicrobials for pigs is imperative to secure animal health and prevent development of critical resistance. An important step in this one-health context is to monitor resistance patterns of important animal pathogens. The aim of this study was to investigate the antimicrobial resistance patterns of five major pathogens in Danish pigs during a period from 2004 to 2017 and elucidate any developments or associations between resistance and usage of antibiotics. RESULTS The minimum inhibitory concentration (MIC) for Escherichia coli, Actinobacillus pleuropneumoniae, Streptococcus suis, Bordetella bronchiseptica, and Staphylococcus hyicus was determined to representatives of antibiotic classes relevant for treatment or surveillance. Escherichia coli isolates were mostly sensitive to fluoroquinolones and colistin, whereas high levels of resistance were observed to ampicillin, spectinomycin, streptomycin, sulfonamides and tetracycline. While resistance levels to most compounds remained relatively stable during the period, resistance to florfenicol increased from 2.1% in 2004 to 18.1% in 2017, likely in response to a concurrent increase in usage. A temporal association between resistance and usage was also observed for neomycin. E. coli serovars O138 and O149 were generally more resistant than O139. For A. pleuropneumoniae, the resistance pattern was homogenous and predictable throughout the study period, displaying high MIC values only to erythromycin whereas almost all isolates were susceptible to all other compounds. Most S. suis isolates were sensitive to penicillin whereas high resistance levels to erythromycin and tetracycline were recorded, and resistance to erythromycin and trimethoprim increasing over time. For S. hyicus, sensitivity to the majority of the antimicrobials tested was observed. However, penicillin resistance was recorded in 69.4-88.9% of the isolates. All B. bronchiseptica isolates were resistant to ampicillin, whereas all but two isolates were sensitive to florfenicol. The data obtained have served as background for a recent formulation of evidence-based treatment guidelines for pigs. CONCLUSIONS Antibiotic resistance varied for some pathogens over time and in response to usage. Resistance to critically important compounds was low. The results emphasize the need for continuous surveillance of resistance patterns also in pig pathogenic bacteria.

中文翻译：

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猪病原细菌的抗生素耐药性及其与抗生素使用的关系。

背景技术对于猪来说，对抗生素的最佳治疗和谨慎使用对于确保动物健康和防止关键耐药性的发展是必不可少的。在这种单一健康的情况下，重要的一步是监视重要动物病原体的耐药模式。这项研究的目的是调查2004年至2017年期间丹麦猪中5种主要病原体的抗药性模式，并阐明抗药性与抗生素使用之间的关系或相关性。结果确定了与治疗或监测相关的抗生素类别代表的大肠杆菌，胸膜肺炎放线杆菌，猪链球菌，支气管博德特氏菌和葡萄球菌的最低抑菌浓度（MIC）。大肠埃希菌分离株对氟喹诺酮类和大肠粘菌素大多敏感，而对氨苄青霉素，壮观霉素，链霉素，磺酰胺和四环素的耐药性较高。虽然在此期间对大多数化合物的抗药性水平保持相对稳定，但对氟苯尼考的​​抗药性从2004年的2.1％增加到2017年的18.1％，这可能是由于同时使用的情况引起的。新霉素的耐药性和使用率之间也存在时间相关性。大肠杆菌血清型O138和O149通常比O139更耐。对于胸膜肺炎链球菌，在整个研究期间耐药模式均一且可预测，仅对红霉素显示高MIC值，而几乎所有分离株均对所有其他化合物敏感。大多数S。猪分离物对青霉素敏感，而记录到的对红霉素和四环素的高抗性水平，并且对红霉素和甲氧苄啶的抗性随时间而增加。对于Hy.us，观察到对大多数测试抗生素的敏感性。但是，在分离株中有69.4-88.9％的青霉素耐药。支气管败血性博德特氏菌的所有分离株均对氨苄西林具有抗药性，而除两个分离株外，所有分离株均对氟苯尼考敏感。所获得的数据已成为最近制定循证治疗猪指南的背景。结论对于某些病原体，抗生素耐药性随时间和使用情况而变化。对至关重要的化合物的抵抗力很低。结果强调了对猪致病菌中耐药性模式的持续监测的必要性。