Food Animal Environmental Systems Research Unit, Agricultural Research Service, U.S. Department of Agriculture, 2413 Nashville Road, B-5, Bowling Green, KY 42101, USA.
Department of Agriculture and Food Science, Western Kentucky University, Bowling Green, KY 42101, USA.
J Food Prot. 2023 Oct;86(10):100144. doi: 10.1016/j.jfp.2023.100144. Epub 2023 Aug 18.
The impact of in-feed use of tylosin in feedlot cattle on Gram-negative foodborne bacteria is unknown. We evaluated the effect of continuous in-feed tylosin use on the concentration and prevalence of tetracycline-resistant (TET)-, third-generation cephalosporin-resistant (3GC)-, and extended-spectrum β-lactamase-producing (ESBLs) E. coli in feedlot cattle. A cohort of weaned calves (10 animals/group) were randomized to receive a feed ration with or without tylosin. Fecal samples, regularly collected over the entire feeding period, and pen surface and feed samples, collected at the end of the feeding period, were cultured on selective media. Enumeration and binary outcomes were analyzed by mixed effects linear regression or logistic regression, respectively, using treatment and days on feed as fixed factors, and animal ID as a random variable. Tylosin supplementation did not affect the fecal concentrations of TETE. coli or fecal prevalence of 3GCE. coli. However, cattle in the tylosin group were 1.5 times more likely (Odds ratio = 1.5: 95% confidence interval: 1.1-2.0) to harbor ESBLs E. coli than the control cattle. Regardless of tylosin treatment, fecal concentrations of TETE. coli and the prevalence of 3GC- and ESBLs-E. coli increased over time. Tylosin-supplemented feed did not affect the prevalence of TETE. coli; 3GC and ESBLs-E. coli were not detected from the feed samples. Most of the 3GC- and ESBLs-E. coli isolates carried the bla gene, widely detected among ESBLs-E. coli human isolates. In summary, although in-feed tylosin use in feedlot cattle did not select for TET- and 3GC-E. coli, it increased the likelihood of detecting ESBL-producing E. coli. Furthermore, the study indicated that the feedlot production setting gradually increases the levels of E. coli resistant to the critically and/or important antibiotics for public health, indicating an increased risk of their dissemination beyond the feedlot environment.
在饲料牛中使用泰乐菌素进行饲料添加对革兰氏阴性食源性病原体的影响尚不清楚。我们评估了连续使用饲料泰乐菌素对饲料牛中四环素耐药（TET）、第三代头孢菌素耐药（3GC）和产超广谱β-内酰胺酶（ESBL）大肠杆菌的浓度和流行率的影响。一组断奶小牛（每组 10 只动物）被随机分配接受含有或不含有泰乐菌素的饲料。在整个饲养期间定期采集粪便样本，在饲养期末采集畜栏表面和饲料样本，并在选择性培养基上培养。使用混合效应线性回归或逻辑回归分别分析计数和二元结果，使用处理和饲养天数作为固定因素，并将动物 ID 作为随机变量。泰乐菌素补充剂并未影响 TETE. coli 的粪便浓度或 3GCE. coli 的粪便流行率。然而，泰乐菌素组的牛携带 ESBLs E. coli 的可能性是对照组的 1.5 倍（优势比=1.5：95%置信区间：1.1-2.0）。无论泰乐菌素治疗如何，TETE. coli 的粪便浓度和 3GC 和 ESBLs-E. coli 的流行率随时间增加。泰乐菌素补充饲料不会影响 TETE. coli 的流行率；从饲料样本中未检测到 3GC 和 ESBLs-E. coli。大多数 3GC 和 ESBLs-E. coli 分离株携带 bla 基因，该基因广泛存在于 ESBLs-E. coli 人分离株中。总之，尽管在饲料牛中使用饲料泰乐菌素并未选择 TET 和 3GC-E. coli，但增加了检测产 ESBLs 的大肠杆菌的可能性。此外，该研究表明，牛场生产环境逐渐增加了对公共卫生至关重要和/或重要的抗生素的大肠杆菌耐药水平，表明其在牛场环境之外传播的风险增加。
