Data about phylogenetic classification of Escherichia coli colonizing calves, lambs and foals are routinely neglected and restricted to outdated methodologies, even in the context of antimicrobial susceptibility (AS) testing. Thus, the aim of this study was to determine the phylogenetic diversity and the AS profile of E. coli colony‐forming units (CFUs) from faecal samples of healthy animals. Five CFUs of E. coli were randomly selected from each faecal culture of calves (n = 13), foals (n = 13) and lambs (n = 13), totalizing 195 CFUs phylo‐typed by quadruplex PCR. The AS profile of five CFUs from 15 samples (five from each animal species; n = 75 isolates) against nine drugs was determined by agar diffusion test. We found E. coli belonging to all phylo‐groups already described, except D group, with the predominance of B1 (65% CFUs; 126/195) in the three‐animal species sampled. Most faecal samples of calves (77%; 10/13) and foals (69%; 9/13) harboured both pathogenic and nonpathogenic E. coli. All faecal samples showed CFUs with diverse AS profile, highlighting the ineffectiveness of tetracycline, sulphonamide and ampicillin. As a key point, our data reinforce the importance to select at least four E. coli CFUs for AS testing.

中文翻译：

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从粪便大肠杆菌中选择特定菌落形成单位的注意事项：它可能不代表样本概况

关于定植小牛、羔羊和小马驹的大肠杆菌系统发育分类数据通常被忽视，并仅限于过时的方法，即使在抗菌药敏 (AS) 测试的背景下也是如此。因此，本研究的目的是确定健康动物粪便样本中大肠杆菌菌落形成单位 (CFU) 的系统发育多样性和 AS 谱。从小牛 (n = 13)、小马驹 (n = 13) 和羔羊 (n = 13) 的每种粪便培养物中随机选择 5 个大肠杆菌 CFU，通过四重 PCR 对总共 195 个 CFU 进行系统分型。通过琼脂扩散试验确定了来自 15 个样本（每个动物物种 5 个；n = 75 个分离株）的 5 个 CFU 对 9 种药物的 AS 曲线。我们发现大肠杆菌属于已经描述的所有系统群，除了 D 组，以 B1 为主（65% CFU；126/195）在采样的三种动物物种中。大多数小牛（77%；10/13）和小马驹（69%；9/13）的粪便样本都含有致病性和非致病性大肠杆菌。所有粪便样本都显示出具有不同 AS 特征的 CFU，突出了四环素、磺胺和氨苄青霉素的无效性。作为一个关键点，我们的数据强调了选择至少四个大肠杆​​菌 CFU 进行 AS 测试的重要性。