Lethbridge Research and Development Centre, Agriculture and Agri-Food Canada, Lethbridge, Alberta, Canada; Department of Biological Sciences, University of Lethbridge, Lethbridge, Alberta, Canada.
Lethbridge Research and Development Centre, Agriculture and Agri-Food Canada, Lethbridge, Alberta, Canada.
Vet Microbiol. 2023 Oct;285:109838. doi: 10.1016/j.vetmic.2023.109838. Epub 2023 Jul 28.
Mycoplasma bovis is an important respiratory pathogen of cattle. In this study, the prevalence and antimicrobial susceptibility of M. bovis were evaluated from two Cohorts of feedlot cattle spanning an 8-year period. In the first study conducted in 2008-2009, nasopharyngeal swabs from cattle sampled at feedlot entry and after 60 days on feed were collected (Cohort 1). In a second study conducted in 2015-2016, nasopharyngeal and trans-tracheal samples were collected from cattle diagnosed with bovine respiratory disease (BRD) and matching healthy controls (Cohort 2). For Cohort 1, the prevalence of M. bovis was lower in cattle at entry compared to when the same individuals were sampled ≥60 days later (P < 0.05). For Cohort 2, the prevalence of M. bovis was greater in both nasopharyngeal and tracheal samples from cattle diagnosed with BRD, compared to controls (P < 0.05). In both Cohorts, almost all isolates were resistant to tilmicosin. Compared to M. bovis from Cohort 1, isolates of Cohort 2 exhibited increased resistance to clindamycin, enrofloxacin, florfenicol, tylosin, and tulathromycin, with the latter showing resistance levels >90 %. These data suggest that antimicrobials used to prevent and treat BRD selected for resistance in M. bovis over the 8-year period. For macrolides, cross-resistance occurred and M. bovis can retain resistance even when antimicrobial selection pressure is removed. Within 9 years of commercial availability of tulathromycin, the majority of M. bovis displayed resistance. Therefore, longitudinal evaluation of resistance in respiratory pathogens is important to ensure efficacious treatment of BRD.
牛支原体是牛的一种重要呼吸道病原体。在这项为期 8 年的研究中，我们评估了来自两个牛饲养场牛群的牛支原体流行率和药敏情况。第一项研究于 2008-2009 年进行，采集牛饲养场入场时和饲养 60 天后的鼻拭子（队列 1）。第二项研究于 2015-2016 年进行，采集患有牛呼吸道疾病（BRD）的牛和匹配的健康对照牛的鼻和气管样本（队列 2）。对于队列 1，与饲养 60 天后采样相比，牛入场时牛支原体的流行率较低（P<0.05）。对于队列 2，与对照组相比，患有 BRD 的牛的鼻和气管样本中牛支原体的流行率更高（P<0.05）。在两个队列中，几乎所有分离株对替米考星均有耐药性。与队列 1 的牛支原体相比，队列 2 的分离株对克林霉素、恩诺沙星、氟苯尼考、泰乐菌素和泰拉霉素的耐药性增加，后者的耐药水平>90%。这些数据表明，在 8 年期间，用于预防和治疗 BRD 的抗生素选择导致了牛支原体的耐药性。对于大环内酯类药物，发生了交叉耐药性，即使去除抗生素选择压力，牛支原体也能保留耐药性。在泰拉霉素上市 9 年内，大多数牛支原体表现出耐药性。因此，对呼吸道病原体的耐药性进行纵向评估对于确保 BRD 的有效治疗非常重要。
