Wang Ou, McAllister Tim A, Plastow Graham, Stanford Kim, Selinger Brent, Guan Le Luo
Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, Canada.
Agriculture and Agri-Food Canada, Lethbridge Research Centre, Lethbridge, AB, Canada.
Appl Environ Microbiol. 2017 Dec 15;84(1). doi: 10.1128/AEM.01738-17. Print 2018 Jan 1.
Cattle are the primary carrier of O157:H7, a foodborne human pathogen, and those shedding >10 CFU/gram of feces of O157:H7 are defined as supershedders (SS). This study investigated the rectoanal junction (RAJ) mucosa-associated microbiota and its relationship with host gene expression in SS and in cattle from which O157:H7 was not detected (nonshedders [NS]), aiming to elucidate the mechanisms involved in supershedding. In total, 14 phyla, 66 families, and 101 genera of RAJ mucosa-associated bacteria were identified and (61.5 ± 7.5%), (27.9 ± 6.4%), and (5.5 ± 2.1%) were the predominant phyla. Differential abundance analysis of operational taxonomic units (OTUs) identified 2 OTUs unique to SS which were members of and and 7 OTUs unique to NS which were members of , , , and Differential abundance analysis of predicted microbial functions (using PICRUSt [phylogenetic investigation of communities by reconstruction of unobserved states]) revealed that 3 pathways had higher abundance (log fold change, 0.10 to 0.23) whereas 12 pathways had lower abundance (log fold change, -0.36 to -0.20) in SS. In addition, we identified significant correlations between expression of 19 differentially expressed genes and the relative abundance of predicted microbial functions, including nucleic acid polymerization and carbohydrate and amino acid metabolism. Our findings suggest that differences in RAJ microbiota at both the compositional and functional levels may be associated with O157:H7 supershedding and that certain microbial groups and microbial functions may influence RAJ physiology of SS by affecting host gene expression. Cattle with fecal O157:H7 at >10 CFU per gram of feces have been defined as the supershedders, and they are responsible for the most of the O157:H7 spread into farm environment. Currently, no method is available for beef producers to eliminate shedding of O157:H7 in cattle, and the lack of information about the mechanisms of supershedding greatly impedes the development of effective methods. This study investigated the role of the rectoanal junction (RAJ) mucosa-associated microbiome in O157:H7 shedding, and our results indicated that the compositions and functions of RAJ microbiota differed between supershedders and nonshedders. The identified relationship between the differentially abundant microbes and 19 previously identified differentially expressed genes suggests the role of host-microbial interactions involved in O157:H7 supershedding. Our findings provide a fundamental understanding of the supershedding phenomenon which is essential for the development of strategies, such as the use of directly fed microbials, to reduce O157:H7 shedding in cattle.
牛是食源性人类病原体O157:H7的主要携带者，每克粪便中O157:H7的排出量>10 CFU的牛被定义为超级排菌者（SS）。本研究调查了直肠肛管连接处（RAJ）黏膜相关微生物群及其与未检测到O157:H7的牛（非排菌者[NS]）的宿主基因表达之间的关系，旨在阐明超级排菌的相关机制。共鉴定出14个门、66个科和101个属的RAJ黏膜相关细菌，其中厚壁菌门（61.5±7.5%）、拟杆菌门（27.9±6.4%）和放线菌门（5.5±2.1%）为优势菌门。对可操作分类单元（OTU）的差异丰度分析确定了2个SS特有的OTU，它们分别属于肠杆菌科和韦荣球菌科，以及7个NS特有的OTU，它们分别属于瘤胃球菌科、理研菌科、梭菌科和毛螺菌科。对预测的微生物功能进行差异丰度分析（使用PICRUSt[通过重建未观察状态对群落进行系统发育研究]）表明，在SS中，有3条通路丰度较高（对数变化倍数为0.10至0.23），而有12条通路丰度较低（对数变化倍数为-0.36至-0.20）。此外，我们确定了19个差异表达基因的表达与预测的微生物功能的相对丰度之间存在显著相关性，包括核酸聚合以及碳水化合物和氨基酸代谢。我们的研究结果表明，RAJ微生物群在组成和功能水平上的差异可能与O157:H7超级排菌有关，并且某些微生物群和微生物功能可能通过影响宿主基因表达来影响SS的RAJ生理学。每克粪便中O157:H7含量>10 CFU的牛被定义为超级排菌者，它们是O157:H7传播到农场环境的主要原因。目前，牛肉生产商没有办法消除牛体内O157:H7的排出，而关于超级排菌机制的信息缺乏极大地阻碍了有效方法的开发。本研究调查了直肠肛管连接处（RAJ）黏膜相关微生物群在O157:H7排出中的作用，我们的结果表明，超级排菌者和非排菌者之间RAJ微生物群的组成和功能存在差异。已确定的差异丰富微生物与19个先前确定的差异表达基因之间的关系表明了宿主-微生物相互作用在O157:H7超级排菌中的作用。我们的研究结果为超级排菌现象提供了基本的理解，这对于制定诸如使用直接投喂微生物等策略以减少牛体内O157:H7的排出至关重要。
