Hirsch Christina, Timsit Edouard, Uddin Muhammed Salah, Guan Le Luo, Alexander Trevor W
Ceva Santé Animale, Libourne, France.
Lethbridge Research and Development Centre, Agriculture and Agri-Food Canada, Lethbridge, AB, Canada.
Front Vet Sci. 2023 Jan 24;9:1026470. doi: 10.3389/fvets.2022.1026470. eCollection 2022.
Bacterial bronchopneumonia (BP) has been associated with purchasing cattle through auction markets. However, whether auction markets are a source of BP-associated bacterial pathogens is unknown. This study evaluated prevalence, antimicrobial susceptibility, and genetic relatedness (using pulsed-field gel electrophoresis, PFGE) of , and isolated from cattle either transported to an auction market prior to feedlot placement (AUC), or directly to a feedlot from a farm (RANC).
Two groups of cattle were enrolled (N = 30 per group) from two separate farms with 15 animals from an individual farm designated as AUC or RANC. Deep nasal swab (DNS) and trans-tracheal aspirates (TTA) were collected on day 0 at weaning (T0) and on day 2 at on-arrival processing at the feedlot (T1). The DNS were also collected on day 9 (T2) and day 30 (T3) after arrival at the feedlot.
In both TTA and DNS, prevalence of bacteria did not differ between AUC and RANC groups ( > 0.05). None of the bacteria isolated at T0 were resistant to antimicrobials and diversity of all bacteria was greatest at T0 and T1. In Group 1 cattle, 100% of isolated at T2 and T3 were multi-drug resistant. These isolates were highly related (>90%) according to PFGE, with most being clones. Though limited in size, results for animals evaluated in this study suggested that auction markets were not a major source of resistant BP pathogens, however, horizontal transmission of a multi-resistant strain of occurred in a feedlot. Spread of resistant was likely due to the selective pressures imposed by feedlot antimicrobial use and encoded resistance by the bacteria.
细菌性支气管肺炎（BP）与通过拍卖市场购买牛有关。然而，拍卖市场是否是与BP相关的细菌病原体的来源尚不清楚。本研究评估了从在饲养场安置前被运至拍卖市场（AUC）或直接从农场运至饲养场（RANC）的牛中分离出的、和的流行率、抗菌药物敏感性及基因相关性（使用脉冲场凝胶电泳，PFGE）。
从两个不同的农场招募两组牛（每组N = 30），每个农场的15只动物被指定为AUC或RANC。在断奶时的第0天（T0）和饲养场入栏处理时的第2天（T1）采集深鼻拭子（DNS）和经气管吸出物（TTA）。在到达饲养场后的第9天（T2）和第30天（T3）也采集DNS。
在TTA和DNS中，AUC组和RANC组之间细菌的流行率没有差异（> 0.05）。在T0分离出的细菌均未对抗菌药物耐药，所有细菌的多样性在T0和T1时最大。在第1组牛中，在T2和T3分离出的100%的对多种药物耐药。根据PFGE，这些分离株高度相关（> 90%），大多数是克隆株。尽管本研究评估的动物数量有限，但结果表明拍卖市场不是耐药BP病原体的主要来源，然而，在一个饲养场中发生了多重耐药菌株的水平传播。耐药的传播可能是由于饲养场使用抗菌药物施加的选择压力以及细菌编码的耐药性。
