Vaccines and Diagnostics Development Programme, ARC-Onderstepoort Veterinary Research, Pretoria.
Onderstepoort J Vet Res. 2020 Jun 24;87(1):e1-e14. doi: 10.4102/ojvr.v87i1.1769.
Three isolates of Ehrlichia ruminantium (Kümm 2, Omatjenne and Riverside), the causative agent of heartwater in domestic ruminants, were isolated in Ixodes scapularis (IDE8) tick cell cultures using the leukocyte fraction of infected sheep blood. All stocks were successfully propagated in IDE8 cells, whereas initiation attempts using endothelial cell cultures were unsuccessful. Therefore, the new technique should be included in any attempt to isolate field strains of E. ruminantium to enhance the probability of getting E. ruminantium isolates which might not be initiated in endothelial cells. Draft genome sequences of all three isolates were generated and compared with published genomes. The data confirmed previous phylogenetic studies that these three isolates are genetically very close to each other, but distinct from previously characterised E. ruminantium isolates. Genome comparisons indicated that the gene content and genomic synteny were highly conserved, with the exception of the membrane protein families. These findings expand our understanding of the genetic diversity of E. ruminantium and confirm the distinct phenotypic and genetic characteristics shared by these three isolates.
三种绵羊无形体（Kümm 2、Omatjenne 和 Riverside）分离株，绵羊无浆体的病原体，通过感染绵羊白细胞的血淋巴在伊氏革蜱（IDE8）细胞中分离得到。所有分离株均在 IDE8 细胞中成功繁殖，而使用内皮细胞培养物进行的起始尝试均未成功。因此，新的技术应包括在尝试分离田间株的任何操作中，以提高获得可能不能在内皮细胞中起始的绵羊无形体分离株的概率。三个分离株的基因组草图序列均已生成，并与已发表的基因组进行了比较。这些数据证实了之前的系统发育研究，这三个分离株在遗传上彼此非常接近，但与之前表征的绵羊无形体分离株不同。基因组比较表明，除了膜蛋白家族外，基因内容和基因组的同线性高度保守。这些发现扩展了我们对绵羊无形体遗传多样性的认识，并证实了这三个分离株共有的独特表型和遗传特征。
