College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA.
J Appl Microbiol. 2018 Mar;124(3):881-898. doi: 10.1111/jam.13679. Epub 2018 Feb 8.
Dairy cattle shed pathogenic Escherichia coli O157 (O157) in faeces, playing a role in human exposure. We aimed to measure faecal microbial communities in early lactation dairy cattle, and model outcomes with O157 shedding metrics.
Daily faecal samples were collected from 40 cattle on two Colorado dairies for five consecutive days, and characterized for O157. 16S rRNA gene sequencing was used to measure sample-level microbial communities. Alpha-diversity metrics were associated with O157 outcomes via regression modelling, adjusting for confounders. Differential abundance of taxa were identified between O157(+) and O157(-) samples and between shedding days of individuals, using matched Wilcoxon rank-sum tests, zero-inflated Gaussian (ZIG) regression and negative binomial regression. After removing an outlier, multi-day and intermittently shedding cows had lower average richness compared to those that never shed. ZIG modelling revealed Bacillus coagulans to be more abundant in O157(-) samples, while Moryella were more abundant in O157(+) samples. Negative binomial models and Wilcoxon tests revealed no differentially abundant taxa between O157(+) vs O157(-) samples, or between shedding days of individuals.
Microbial diversity and some taxa may be influenced by or affect O157 shedding by dairy cattle.
If future work corroborates these findings, dairy cow microbial community changes may be used to guide on-farm strategies that mitigate O157 dissemination, protecting the human food chain.
奶牛粪便中会排出致病性大肠杆菌 O157（O157），从而使人接触到该病菌。本研究旨在测量泌乳早期奶牛粪便中的微生物群落，并建立与 O157 排出量相关的模型。
我们连续五天从科罗拉多州的两个奶牛场采集了 40 头奶牛的每日粪便样本，并对 O157 进行了检测。使用 16S rRNA 基因测序来测量样本水平的微生物群落。通过回归模型，调整混杂因素，将α多样性指标与 O157 的结果相关联。使用匹配的 Wilcoxon 秩和检验、零膨胀高斯（ZIG）回归和负二项回归，在去除离群值后，比较 O157（+）和 O157（-）样本以及个体排菌天数之间的分类群丰度差异。多日和间歇性排菌的奶牛的平均丰富度低于从未排菌的奶牛。ZIG 模型显示凝结芽孢杆菌在 O157（-）样本中更为丰富，而 Moryella 在 O157（+）样本中更为丰富。负二项模型和 Wilcoxon 检验显示，O157（+）与 O157（-）样本之间以及个体排菌天数之间不存在丰度差异的分类群。
微生物多样性和一些分类群可能受到奶牛 O157 排出的影响，或者影响 O157 的排出。
如果未来的研究证实了这些发现，那么奶牛微生物群落的变化可能被用于指导农场策略，以减轻 O157 的传播，保护人类食物链。
