Swine dysentery, caused by Brachyspira hyodysenteriae and the newly recognized Brachyspira hampsonii in grower-finisher pigs, is a substantial economic burden in many swine-rearing countries. Antimicrobial therapy is the only commercially available measure to control and prevent Brachyspira-related colitis. However, data on antimicrobial susceptibility trends and genetic diversity of Brachyspira species from North America is limited. We evaluated the antimicrobial susceptibility profiles of U.S. Brachyspira isolates recovered between 2013 and 2022 to tiamulin, tylvalosin, lincomycin, doxycycline, bacitracin, and tylosin. In addition, we performed multilocus sequence typing (MLST) on 64 B. hyodysenteriae isolates. Overall, no distinct alterations in the susceptibility patterns over time were observed among Brachyspira species. However, resistance to the commonly used antimicrobials was seen sporadically with a higher resistance frequency to tylosin compared to other tested drugs. B. hampsonii was more susceptible to the tested drugs than B. hyodysenteriae and B. pilosicoli. MLST revealed 16 different sequence types (STs) among the 64 B. hyodysenteriae isolates tested, of which 5 STs were previously known, whereas 11 were novel. Most isolates belonged to the known STs: ST93 (n = 32) and ST107 (n = 13). Our findings indicate an overall low prevalence of resistance to clinically important antimicrobials other than tylosin and bacitracin, and high genetic diversity among the clinical Brachyspira isolates from pigs in the United States during the past decade. Further molecular, epidemiologic, and surveillance studies are needed to better understand the infection dynamics of Brachyspira on swine farms and to help develop effective control measures.

中文翻译：

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通过多位点序列分型研究美国猪短螺旋体分离株的抗菌敏感性和猪痢疾短螺旋体的遗传多样性。

猪痢疾是由猪痢疾短螺旋体和新近发现的汉普氏短螺旋体在生长肥育猪中引起的，是许多养猪国家的沉重经济负担。抗菌治疗是控制和预防短螺旋体相关结肠炎的唯一商业化措施。然而，关于北美短螺旋体物种的抗菌药物敏感性趋势和遗传多样性的数据有限。我们评估了 2013 年至 2022 年间回收的美国短螺旋体分离株对泰妙菌素、泰万菌素、林可霉素、多西环素、杆菌肽和泰乐菌素的抗菌敏感性。此外，我们对 64 株猪痢疾短螺旋体分离株进行了多位点序列分型 (MLST)。总体而言，随着时间的推移，短螺旋体物种的敏感性模式没有观察到明显的变化。然而，与其他测试药物相比，对常用抗菌药物的耐药性偶尔出现，对泰乐菌素的耐药频率更高。汉普氏芽孢杆菌比猪痢疾芽孢杆菌和毛状芽胞杆菌对测试药物更敏感。MLST揭示了测试的64个猪痢疾短螺旋体分离株中的16种不同的序列类型(ST)，其中5个ST是先前已知的，而11个是新的。大多数分离株属于已知的 ST：ST93 (n = 32) 和 ST107 (n = 13)。我们的研究结果表明，过去十年，美国猪的临床短螺旋体分离株对泰乐菌素和杆菌肽以外的临床重要抗菌药物的耐药率总体较低，且遗传多样性较高。需要进一步的分子、流行病学和监测研究，以更好地了解养猪场短螺旋体的感染动态，并帮助制定有效的控制措施。