Emerging Pathogens Institute, University of Florida, Gainesville, FL, 32611, USA.
Department of Animal Sciences, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL, 32611, USA.
Appl Microbiol Biotechnol. 2021 Mar;105(5):2109-2121. doi: 10.1007/s00253-021-11167-4. Epub 2021 Feb 15.
Intramammary bacterial infection, the most common cause of mastitis, is the most costly disease in dairy cattle in the US and reason for antibiotic usage. Ceftiofur, a third-generation cephalosporin, is generally used to treat such disease, but it has a high treatment failure rate. Though the reason is not known clearly, it is hypothesized that multiple factors are associated with the treatment failure. In this study, we analyzed 169 milk samples from cows with mastitis in two independent dairy farms (Farm A and B) in which 19.4% (Farm A) and 14.3% (Farm B) of the antibiotic treated cows were not cured. The prevalence of cephalosporin-resistant bacteria (CRB) in milk was 72.0% and 42.1% in Farm A and B, respectively. Nineteen and nine bacterial genera were identified in Farm A and B respectively, with the most abundant genus being Staphylococcus (27.1%; Farm A) and Bacillus (63.5%; Farm B). However, no strong relationship between the treatment failure rate and the CRB prevalence was observed. Furthermore, the metagenomic analysis showed no significant differences in the α- and β-diversities of microbiota in milk samples from cured and uncured cows, suggesting that antibiotic-resistant bacteria were not the sole reason for the antibiotic treatment failure. KEY POINTS: • The mastitic milk samples had high prevalence of cephalosporin-resistant bacteria (CRB). • The CRB identified belong to diversified species. • Antibiotic treatment failure was not solely caused by the abundance of CRB.
乳腺内细菌感染是乳腺炎最常见的病因，也是美国奶牛养殖业中最昂贵的疾病，也是抗生素使用的原因。头孢噻呋是一种第三代头孢菌素，通常用于治疗此类疾病，但治疗失败率很高。虽然原因尚不清楚，但据推测与多种因素有关。在这项研究中，我们分析了来自两个独立奶牛场（A 场和 B 场）乳腺炎奶牛的 169 份牛奶样本，其中 19.4%（A 场）和 14.3%（B 场）接受抗生素治疗的奶牛未治愈。牛奶中头孢菌素耐药菌（CRB）的流行率分别为 72.0%和 42.1%，在 A 场和 B 场分别鉴定出 19 种和 9 种细菌属，最丰富的属分别为葡萄球菌（27.1%；A 场）和芽孢杆菌（63.5%；B 场）。然而，治疗失败率与 CRB 流行率之间没有很强的关系。此外，宏基因组分析显示，治愈和未治愈奶牛的牛奶样本中微生物群的α和β多样性没有显著差异，这表明抗生素耐药菌不是抗生素治疗失败的唯一原因。关键点：
乳腺炎牛奶样本中头孢菌素耐药菌（CRB）的流行率很高。
鉴定出的 CRB 属于多样化的物种。
抗生素治疗失败不仅仅是由于 CRB 的丰度引起的。
