Mir Raies A, Schaut Robert G, Looft Torey, Allen Heather K, Sharma Vijay K, Kudva Indira T
Food Safety and Enteric Pathogens Research Unit, National Animal Disease Center, Agricultural Research Service, United States Department of Agriculture, Ames, IA, United States.
ARS Research Participation Program, Oak Ridge Institute for Science and Education (ORISE), Oak Ridge, TN, United States.
Front Microbiol. 2020 Apr 17;11:693. doi: 10.3389/fmicb.2020.00693. eCollection 2020.
Cattle are the asymptomatic reservoirs of O157:H7 (O157) that preferentially colonizes the bovine recto-anal junction (RAJ). Understanding the influence of O157 on the diversity of the RAJ microbiota could give insights into its persistence at the RAJ in cattle. Hence, we compared changes in bovine RAJ and fecal microbiota following O157 challenge under experimental conditions. Cattle were either orally challenged ( = 4) with10 CFU of a streptomycin-resistant O157 strain 86-24, or mock-challenged ( = 4) with phosphate buffered saline. Rectoanal mucosal swab (RAMS) and fecal samples were collected at different time points for analysis. Alpha diversity measures (Chao1 species richness and Shannon diversity index) were found to be significantly different between RAMS and fecal samples but not influenced by O157 challenge. The to (F: B) ratio was higher in RAMS samples from O157 colonized animals and this may have influenced the consistent yet decreased O157 colonization at the RAJ. Specific bacterial genera that were present in relative low abundance in fecal and RAMS microbiota did not affect overall microbial diversity but were associated with O157 colonization. Differential abundance analysis (DAA) of genera in samples from O157 shedding cattle indicated significantly higher relative abundance of and in RAMS, and in fecal samples. Mock-challenged cattle showed higher relative abundance of and in RAMS samples, and , and in fecal samples. These results suggest that O157 challenge exerts transient influence on the intestinal microbial community which in turn might promote O157 colonization in a site-specific manner.
牛是O157:H7（O157）的无症状宿主，该病菌优先定殖于牛的直肠肛门交界处（RAJ）。了解O157对RAJ微生物群多样性的影响，有助于深入了解其在牛RAJ处的持久性。因此，我们在实验条件下比较了O157攻击后牛RAJ和粪便微生物群的变化。牛要么口服10 CFU耐链霉素的O157菌株86 - 24进行攻击（n = 4），要么用磷酸盐缓冲盐水进行模拟攻击（n = 4）。在不同时间点收集直肠肛门黏膜拭子（RAMS）和粪便样本进行分析。发现RAMS和粪便样本之间的α多样性指标（Chao1物种丰富度和香农多样性指数）存在显著差异，但不受O157攻击的影响。来自O157定殖动物的RAMS样本中F:B比例较高，这可能影响了O157在RAJ处持续但减少的定殖。在粪便和RAMS微生物群中相对丰度较低的特定细菌属不影响整体微生物多样性，但与O157定殖有关。对O157排毒牛样本中的属进行差异丰度分析（DAA）表明，RAMS中Turicibacter和Sphingobacterium的相对丰度显著较高，粪便样本中Ruminococcus相对丰度显著较高。模拟攻击的牛在RAMS样本中Ruminococcus、Bacteroides和Prevotella的相对丰度较高，在粪便样本中Butyrivibrio、Ruminococcus和Faecalibacterium的相对丰度较高。这些结果表明，O157攻击对肠道微生物群落产生短暂影响，进而可能以位点特异性方式促进O157定殖。
