Laboratories of The Rockefeller Institute for Medical Research.
J Exp Med. 1926 Mar 31;43(4):515-32. doi: 10.1084/jem.43.4.515.
A systematic study of 74 ticks, the infectivity or non-infectivity of which was determined by biting experiments, inoculation of emulsions, and specific immunity tests, showed the presence in some instances of several types of microorganisms morphologically resembling the inciting microorganism of spotted fever. The most frequently isolated was B. rickettsiformis, n. sp., those less commonly encountered were B. pseudoxerosis, n. sp., and B. equidistans, n. sp. These organisms are non-pathogenic for the guinea pig, rabbit, and Macacus rhesus. In morphological features they resemble the forms found in smears and sections of the ticks, yet their presence had no relation to infectivity. Immunologically they are not related to the spotted fever virus. All three are pleomorphic under cultural conditions, and the question arises whether or not the minute non-pathogenic Rickettsia forms and the somewhat coarser symbionts found in Dermacentor andersoni are morphological variations due to variations in nutrition, oxygen tension, tissue reactions, etc., in the different tissues and cells in which the organisms are embedded. At all events, the differentiation of the non-pathogenic Rickettsia-like organisms from Dermacentroxenus rickettsi is extremely difficult. In definitely infective ticks of the present study intranuclear forms were not constant. A point of special interest is that these non-pathogenic micro-organisms from ticks grow best at room temperature, in this respect resembling culturally certain flagellates inhabiting the alimentary tract of insects. The difficulty of obtaining initial growth on artificial media and the gradual adaptation to less specialized media are other notable characteristics of these organisms. The possibility that B. rickettsiformis is a non-pathogenic phase of the spotted fever organism, comparable with the avirulent flagellate culture forms of Leishmanias, seems remote in view of the negative immunological findings. Hereditary transmission of B. rickettsiformis is clearly indicated by its presence in large numbers in ovaries and egg cells, a characteristic also of the spotted fever organism and of other insect-borne Rickettsiae.
对 74 只蜱进行了系统研究，通过叮咬实验、接种乳剂和特异性免疫试验确定了它们的感染性或非感染性，结果发现某些情况下存在几种形态上类似于斑疹热致病微生物的微生物。最常分离到的是 B. rickettsiformis，n. sp.，较少分离到的是 B. pseudoxerosis，n. sp. 和 B. equidistans，n. sp. 这些生物体对豚鼠、兔和恒河猴均无致病性。在形态特征上，它们与在蜱的涂片和切片中发现的形态相似，但它们的存在与感染性无关。免疫上它们与斑疹热病毒无关。在培养条件下，它们都呈多形性，因此出现了一个问题，即是否是由于营养、氧张力、组织反应等因素的变化，导致在 Dermacentor 和ersoni 中发现的微小非致病性立克次体形态和稍大的共生体发生了形态变异。无论如何，非致病性类立克次体与 Dermacentroxenus rickettsi 的分化极其困难。在本研究中具有明确感染性的蜱中，核内形态并不稳定。一个特别有趣的观点是，这些来自蜱的非致病性微生物在室温下生长最好，这在某种程度上类似于栖息在昆虫消化道中的某些文化性鞭毛生物。在人工培养基上获得初始生长的困难以及对较少专门培养基的逐渐适应是这些生物体的其他显著特征。鉴于免疫学方面的阴性发现，B. rickettsiformis 是一种类似于斑疹热病原体的非致病性阶段，类似于无毒性的鞭毛生物培养形式的利什曼原虫，这种可能性似乎不大。B. rickettsiformis 在卵巢和卵细胞中大量存在，这表明其具有遗传性，这一特征也存在于斑疹热病原体和其他昆虫传播的立克次体中。
