Abstract：
Digital dermatitis (DD) is an ulcerative foot lesion on the heel bulbs of dairy cattle. DD is a polymicrobial disease with no precise etiology, although Treponema spirochetes are found disproportionally abundant in diseased tissue. Within Treponema, several different species are found in DD; however, the species Treponema phagedenis is uniformly found in copious quantities and deep within the skin layers of the active, ulcerative stages of disease. The pathogenic mechanisms these bacteria use to persist in the skin and the precise role they play in the pathology of DD are widely unknown. To explore the pathogenesis and virulence of Treponema phagedenis, newly isolated strains of this species were investigated in a subcutaneous murine abscess model. In the first trial, a dosage study was conducted to compare the pathogenicity of different strains across three different treponemes per inoculum (TPI) doses based on abscess volumes. In the second trial, the expression levels of 11 putative virulence genes were obtained to gain insight into their involvement in pathogenesis. During the RT-qPCR analysis, it was determined that genes encoding for two metal-ion import lipoproteins and two adherence genes were found highly upregulated during infection. Conversely, two genes involved in motility and chemotaxis were found to not be significantly upregulated or utilized during infection. These results were supported by gene expression data from natural M2 lesions of dairy cattle. This gene expression analysis could highlight the preference in strategy for T. phagedenis to persist and adhere in the host rather than engage in motility and disseminate.
摘要：
数字皮炎（DD）是奶牛足跟鳞茎上的溃疡性足部病变。DD是一种多微生物疾病，没有确切的病因，尽管在患病组织中发现螺旋体螺旋体异常丰富。在密螺旋体内，在DD中发现了几种不同的物种；然而，在活性物质的皮肤层深处，疾病的溃疡性阶段。这些细菌在皮肤中持续存在的致病机制以及它们在DD病理中的确切作用尚不清楚。探讨螺旋体的致病机理和毒力,在皮下鼠脓肿模型中研究了该物种的新分离菌株。在第一次审判中,我们进行了一项剂量研究,根据脓肿体积,比较了3种不同螺旋体/接种物(TPI)剂量中不同菌株的致病性.在第二次审判中,获得了11个推定的毒力基因的表达水平，以了解它们在发病机理中的参与。在RT-qPCR分析过程中，确定了编码两种金属离子导入脂蛋白和两种贴壁基因的基因在感染期间高度上调.相反，在感染过程中，发现两个与运动性和趋化性有关的基因未被显著上调或利用。这些结果得到来自奶牛天然M2病变的基因表达数据的支持。这种基因表达分析可以突出表明T.phagedenis在宿主中持续和粘附而不是从事运动性和传播的策略偏好。
