Aims: 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.
Methods and results: 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.
Conclusions: Microbial diversity and some taxa may be influenced by or affect O157 shedding by dairy cattle.
Significance and impact of the study: 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.
Keywords: Escherichia coli O157; dairy; ecology; epidemiology; modelling.
© 2017 The Society for Applied Microbiology.