Department of Animal Science, University of Manitoba, Winnipeg, MB, Canada R3T 2N2.
Department of Production Animal Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada.
J Dairy Sci. 2018 Nov;101(11):10191-10205. doi: 10.3168/jds.2018-14858. Epub 2018 Aug 29.
Antimicrobial dry cow therapy (DCT) is an important component of mastitis control programs aimed to eliminate existing intramammary infections and prevent the development of new ones during the dry period. However, to what extent the microbiota profiles of different niches of the udder change during the dry period and following administration of DCT remains poorly understood. Therefore, the main objective of the present study was to qualitatively evaluate dynamics of the microbiota of teat canal (TC) and mammary secretions (i.e., milk and colostrum) of healthy udder quarters subjected to DCT using a long-acting antimicrobial product, containing penicillin G and novobiocin, in combination with internal teat sealant. To this end, TC swabs (n = 58) and their corresponding milk (n = 29) and colostrum samples (n = 29) were collected at the time of drying off and immediately after calving from clinically healthy udder quarters of Holstein dairy cows from a commercial dairy farm. All samples were subjected to DNA extraction and high-throughput sequencing of the V1-V2 hypervariable regions of bacterial 16S rRNA genes. Overall, shifts were more pronounced within the microbiota of mammary secretions than the TC. In particular, microbiota of colostrum samples collected immediately after calving were less species-rich compared with the pre-DCT milk samples. Proportions of several bacterial genera belonging to the phylum Proteobacteria, including Pseudomonas, Stenotrophomonas, and unclassified Alcaligenaceae, were enriched within the microbiota of colostrum samples, whereas Firmicutes genera, including Butyrivibrio, unclassified Clostridiaceae, and unclassified Bacillales, were overrepresented in pre-DCT milk microbiota. Apart from shifts in the proportion of main bacterial genera and phyla, qualitative analysis revealed a high degree of commonality between pre-DCT and postpartum microbiota of both niches of the udder. Most importantly, a considerable number of bacterial genera and species commonly regarded as mastitis pathogens or opportunists (or both), including Staphylococcus spp., unclassified Enterobacteriaceae, and Corynebacterium spp., were shared between pre-DCT and postpartum microbiota of mammary secretions. Percentage of shared bacterial genera and species was even higher between pre-DCT and postpartum microbiota of TC samples, suggesting that the DCT approach of the present study had limited success in eliminating a considerable proportion of bacteria during the dry period.
抗菌干奶牛疗法（DCT）是乳腺炎控制计划的重要组成部分，旨在消除现有的乳房内感染，并防止在干奶期发生新的感染。然而，在干奶期和 DCT 给药后，不同乳区的微生物群谱在何种程度上发生变化仍知之甚少。因此，本研究的主要目的是使用长效抗菌产品（含有青霉素 G 和新生霉素）联合内部乳头密封剂，定性评估健康乳区乳头管（TC）和乳腺分泌物（即牛奶和初乳）的微生物群动态。为此，在从商业奶牛场的荷斯坦奶牛的临床健康乳区挤奶结束时和产犊后立即收集 TC 拭子（n = 58）及其相应的牛奶（n = 29）和初乳样本（n = 29）。所有样本均进行 DNA 提取，并对细菌 16S rRNA 基因的 V1-V2 高变区进行高通量测序。总体而言，TC 内的微生物群变化比乳腺分泌物更明显。特别是，产犊后立即采集的初乳样本的物种丰富度低于 DCT 前的牛奶样本。属于变形菌门的几个细菌属的比例增加，包括假单胞菌、寡养单胞菌和未分类的产碱杆菌科，在初乳样本的微生物群中富集，而厚壁菌门的属，包括丁酸梭菌、未分类的梭菌科和未分类的芽孢杆菌科，在 DCT 前的牛奶微生物群中过度表达。除了主要细菌属和门的比例变化外，定性分析还揭示了两个乳区 DCT 前和产后微生物群之间的高度共性。最重要的是，相当数量的通常被认为是乳腺炎病原体或机会主义者（或两者兼有）的细菌属和种，包括金黄色葡萄球菌、未分类的肠杆菌科和棒状杆菌属，在 DCT 前和产后的乳腺分泌物微生物群中共享。TC 样本的 DCT 前和产后微生物群中共享细菌属和种的比例甚至更高，这表明本研究的 DCT 方法在干奶期消除相当一部分细菌的效果有限。
