Department of Veterinary Medicine and Epidemiology, University of California, School of Veterinary Medicine, Davis, California, United States of America.
Veterinary Medicine Teaching and Research Center, School of Veterinary Medicine, University of California Davis, Tulare, California, United States of America.
PLoS One. 2021 Nov 24;16(11):e0260292. doi: 10.1371/journal.pone.0260292. eCollection 2021.
Antimicrobial drug (AMD) use for bovine respiratory disease (BRD) continues to be concerning for development of antimicrobial resistance (AMR) in respiratory and enteric bacteria of cattle. This study aimed to provide data regarding AMR in respiratory isolates, and identify relationships between respiratory and enteric AMD susceptibility, in weaned dairy heifers. A cross-sectional study was performed between June of 2019 and February 2020, on 6 calf rearing facilities in California. Deep nasopharyngeal and rectal swabs were collected from 341 weaned heifers and submitted for selective bacterial culture and AMR testing. Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni were selectively isolated from respiratory samples; Escherichia coli and Enterococcus spp. were selectively isolated from rectal swabs. Minimum inhibitory concentrations (MIC) were determined for selected isolates against 19 AMD. The proportion of resistant isolates was calculated using Clinical Laboratory Standards Institute (respiratory) or USDA NARMS (enteric) breakpoints; when no applicable breakpoint was available, the distribution of MIC was described and compared. Association between AMR in a calf's respiratory isolate and a higher or lower MIC of the matched enteric isolates was determined. More than 50% of P. multocida isolates were resistant to each of 7 AMD commonly used to treat BRD (florfenicol, gamithromycin, tildipirosin, tilmicosin, danofloxacin, enrofloxacin and tetracycline). Resistance in respiratory isolates was only associated with higher matched enteric MIC for gamithromycin and tulathromycin. Multidrug resistance was reported in >70% of P. multocida and M. haemolytica isolates. Antimicrobial resistance, including multidrug resistance, in respiratory isolates appears to be widespread in weaned dairy heifers; this finding has not previously been reported and raises concern for the future efficacy of AMD used to treat respiratory diseases in weaned dairy heifers. Enteric bacterial MIC appear to have limited direct association with respiratory isolate AMR classification.
用于治疗牛呼吸道疾病（BRD）的抗菌药物（AMD）的使用持续引发人们对牛呼吸系统和肠道细菌产生抗菌药物耐药性（AMR）的担忧。本研究旨在提供有关呼吸道分离株的 AMR 数据，并确定断奶奶牛犊牛的呼吸道和肠道 AMD 敏感性之间的关系。本研究为横断面研究，于 2019 年 6 月至 2020 年 2 月期间在加利福尼亚州的 6 个犊牛饲养场进行。从 341 头断奶奶牛犊牛中采集了深部鼻咽和直肠拭子，并进行了选择性细菌培养和 AMR 检测。从呼吸道样本中选择性分离出了溶血曼海姆菌、多杀巴斯德菌和溶血性嗜血杆菌；从直肠拭子中选择性分离出了大肠杆菌和肠球菌属。针对 19 种 AMD 确定了选定分离株的最低抑菌浓度（MIC）。使用临床和实验室标准协会（respiratory）或美国农业部国家抗微生物监测系统（enteric）的折点计算耐药分离株的比例；当没有适用的折点时，描述并比较 MIC 分布。确定了牛犊呼吸道分离株的 AMR 与匹配肠道分离株的更高或更低 MIC 之间的关系。超过 50%的多杀巴斯德菌分离株对 7 种常用于治疗 BRD 的 AMD（氟苯尼考、加米霉素、替米考星、替米考星、达氟沙星、恩诺沙星和四环素）均具有耐药性。呼吸道分离株的耐药性仅与加米霉素和酒石酸泰乐菌素的更高匹配肠道 MIC 相关。超过 70%的多杀巴斯德菌和溶血曼海姆菌分离株报告了多重耐药性。在断奶奶牛犊牛中，呼吸道分离株的抗菌药物耐药性（包括多重耐药性）似乎广泛存在；这一发现以前尚未报道过，令人担忧的是，未来用于治疗断奶奶牛犊牛呼吸道疾病的 AMD 的疗效。肠道细菌的 MIC 与呼吸道分离株的 AMR 分类似乎没有直接的关联。
