Antibiotic resistance represents a growing crisis in both human and veterinary medicine. We evaluated the use of antibiotic alternatives—heavy metals and essential oils—in beef cattle feeding, and their effects on Gram-negative and Gram-positive bacteria. In this randomized controlled field trial, we measured the impact of supplemental zinc and menthol on antibiotic resistance among commensal enteric bacteria of feeder cattle. Fecal suspensions were plated onto plain- and antibiotic-supplemented MacConkey and m-Enterococcus agar for quantification of total and antibiotic-resistant Escherichia coli and Enterococcus spp., respectively. Temporal effects on overall E. coli growth were significant (p < 0.05), and menthol was associated with decreased growth on tetracycline-supplemented agar. Zinc was associated with significant increases in growth on erythromycin-supplemented m-Enterococcus agar. Cattle fed zinc exhibited significantly higher levels of macrolide resistance among fecal enterococci isolates.

中文翻译：

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锌和薄荷醇饮食对大肠杆菌和肠球菌属抗生素抗性共选的影响。在牛

抗生素耐药性代表着人类医学和兽医学中日益严重的危机。我们评估了在肉牛饲养中使用抗生素替代品（重金属和精油）及其对革兰氏阴性和革兰氏阳性细菌的影响。在这项随机对照的田间试验中，我们测量了补锌和薄荷醇对饲养牛共生肠细菌中抗生素耐药性的影响。将粪便悬浮液铺在补充了普通和抗生素的MacConkey和m-肠球菌琼脂上，分别定量总的和抗药性的大肠杆菌和肠球菌。时间对大肠杆菌总体生长的影响显着（p<0.05），并且薄荷醇与补充四环素的琼脂的生长下降有关。锌与补充红霉素的间肠球菌琼脂的生长显着增加有关。在粪便肠球菌分离物中，饲喂牛的锌对大环内酯类药物的抵抗力明显更高。