Purpose : Because cattle mount no O157 immune response and have uniform diets and environmental exposures, we hypothesized that the structure of the colonic microbial community influences a given animal’s risk of shedding O157. The current study aimed to measure these microbial communities in early lactation dairy cattle, and model outcomes with O157 shedding metrics.
Methods : Cattle feces were collected from 40 O157 shedding and nonshedding dairy cattle on two farms over the course of five days. Samples were characterized for O157 using standard laboratory detection techniques. Based on detection, individual samples were classified for presence or absence of O157 and study cattle were classified by O157 shedding pattern (never, intermittent, multiday) and ever versus never shedding. 16s rRNA sequencing was used to measure microbial community composition. Alpha diversity metrics (richness, evenness and Shannon’s index) were quantified and associated with shedding outcomes via regression modeling, adjusting for covariates previously seen to influence O157 shedding status (parity, days in milk, disease, farm and disease treatment). Differential abundances of bacterial taxa were identified between O157 positive and negative samples using zero-inflated Gaussian models.
Results : A total of 196 samples were analyzed for O157 presence. When outcomes were modeled with alpha diversity measures, multiday shedding animals were seen to have significantly lower richness than those that never shed O157. Zero-inflated modeling revealed 3 taxa more abundant in nonO157 samples: Bacillus coagulans, Blautia producta, and Clostridium neonatale. Moryella indoligenes, meanwhile, was seen to be more abundant in O157 positive samples.
Significance : These results indicate that both microbial diversity and some key taxa may influence O157 shedding of healthy dairy cattle. Understanding these microbial community changes may be used to guide on-farm strategies that mitigate O157 dissemination, ultimately protecting the human food chain.