Jongejan F, Zandbergen T A, van de Wiel P A, de Groot M, Uilenberg G
Department of Tropical Veterinary Medicine and Protozoology, Institute of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht, The Netherlands.
Onderstepoort J Vet Res. 1991 Dec;58(4):227-37.
The development of the tick-borne rickettsial pathogen Cowdria ruminantium (S stock) was studied in bovine umbilical endothelial (BUE) cell cultures and in goat choroid plexus, by light- and electron microscopy. Cowdria divided by binary fission within intracytoplasmic vacuoles resulting in large colonies of reticulate bodies. After three to four days in culture, reticulate bodies developed into smaller intermediate bodies characterized by an electron-dense core. Shortly before disruption of the host cells, intermediate bodies condensed further into electron-dense elementary bodies, which were released into the culture medium. Elementary bodies invade other endothelial cells thus initiating a new infectious cycle which lasts between 5 and 6 days. In the infected goat choroid plexus similar reticulate and intermediate bodies were identified within vacuoles of capillary endothelial cells. However, extracellular elementary bodies were not detected. Another stock of Cowdria (W) showed an identical developmental cycle as that of the S stock. The W isolate was also pathogenic for mice, making it possible to test the infectivity of reticulate and elementary bodies in these animals. Reticulate bodies appeared to be less infective than elementary bodies. The developmental cycle of Cowdria resembles the cycle known to occur in Chlamydia. Moreover, Cowdria has other similarities with Chlamydia. It has a Gram-negative envelope, it does not store iodine-stainable carbohydrates and may lack peptidoglycan as does Chlamydia. It is concluded, that Cowdria and Chlamydia are to a certain extent related, confirming a recent report that both organisms have certain antigenic determinants in common. Since Cowdria is also related to Ehrlichia it may well be that Cowdria takes an intermediate position between Chlamydia and Ehrlichia. The phylogenetic relationship between Cowdria and Chlamydia and also with Ehrlichia should be further elucidated by molecular analysis using 16S ribosomal DNA sequences.
利用光镜和电镜技术，对蜱传立克次氏体病原体反刍兽考德里氏体（S株）在牛脐静脉内皮（BUE）细胞培养物及山羊脉络丛中的发育情况进行了研究。考德里氏体在胞质内空泡中通过二分裂进行繁殖，形成大量网状体菌落。培养三到四天后，网状体发育成较小的中间体，其特征为电子致密核心。在宿主细胞破裂前不久，中间体进一步浓缩成电子致密的原体，释放到培养基中。原体侵入其他内皮细胞，从而启动一个持续5至6天的新感染周期。在感染的山羊脉络丛中，在毛细血管内皮细胞的空泡内发现了类似的网状体和中间体。然而，未检测到细胞外原体。考德里氏体的另一株（W株）显示出与S株相同的发育周期。W株分离物对小鼠也具有致病性，这使得在这些动物中测试网状体和原体的感染性成为可能。网状体的感染性似乎低于原体。考德里氏体的发育周期类似于已知在衣原体中发生的周期。此外，考德里氏体与衣原体还有其他相似之处。它具有革兰氏阴性包膜，不储存碘染色的碳水化合物，可能像衣原体一样缺乏肽聚糖。得出的结论是，考德里氏体和衣原体在一定程度上相关，这证实了最近的一份报告，即这两种生物体有某些共同的抗原决定簇。由于考德里氏体也与埃立克体有关，很可能考德里氏体处于衣原体和埃立克体之间的中间位置。考德里氏体与衣原体以及与埃立克体之间的系统发育关系应通过使用16S核糖体DNA序列的分子分析进一步阐明。
