Dumler J S, Chen S M, Asanovich K, Trigiani E, Popov V L, Walker D H
Department of Pathology, University of Maryland Medical Center, Baltimore 21201, USA.
J Clin Microbiol. 1995 Jul;33(7):1704-11. doi: 10.1128/jcm.33.7.1704-1711.1995.
Ehrlichia chaffeensis is the causative agent of human monocytic ehrlichiosis, a disease that ranges in severity from asymptomatic infection to death. Only one isolate of E. chaffeensis has been made, the Arkansas strain, upon which all characterizations of the agent of human monocytic ehrlichiosis have been based. We report the isolation and characterization of a new strain of E. chaffeensis, the 91HE17 strain, which was cultivated from a patient with a nearly fatal illness. The new isolate grows best in culture with careful control of pH. The two isolates are nearly identical as determined by light and electron microscopy and have significant antigenic identity in fluorescent-antibody and immunoblot assays using polyclonal antisera and the E. chaffeensis-specific monoclonal antibody 1A9. Isolate 91HE17 had 99.9% nucleotide sequence identity with the Arkansas strain in the 16S rRNA gene. Parts of the Escherichia coli GroE operon homologs had identical restriction enzyme digestion patterns, and a 425-bp region of the GroEL gene had at least 99.8% sequence identity between the E. chaffeensis Arkansas and 91HE17 strains. Isolate 91HE17 lacked an epitope identified in E. chaffeensis Arkansas by the monoclonal antibody 6A1. This new E. chaffeensis isolate is very similar to the Arkansas strain and provides the opportunity to substantiate the existence of diversity among ehrlichiae which infect humans. Specific factors which differ among strains may then be compared to assess their potential contributions toward cellular pathogenicity and ultimately toward the development of disease in humans.
恰菲埃立克体是人类单核细胞埃立克体病的病原体，该疾病严重程度不一，从无症状感染到死亡。恰菲埃立克体仅获得了一株分离株，即阿肯色菌株，人类单核细胞埃立克体病病原体的所有特征描述均基于此。我们报告了一株新的恰菲埃立克体菌株91HE17的分离和特征描述，该菌株是从一名患有近乎致命疾病的患者身上培养出来的。新分离株在仔细控制pH值的培养条件下生长最佳。通过光学显微镜和电子显微镜观察，这两株分离株几乎相同，并且在使用多克隆抗血清和恰菲埃立克体特异性单克隆抗体1A9的荧光抗体和免疫印迹试验中具有显著的抗原同一性。在16S rRNA基因中，分离株91HE17与阿肯色菌株的核苷酸序列同一性为99.9%。大肠杆菌GroE操纵子同源物的部分具有相同的限制性内切酶消化模式，并且恰菲埃立克体阿肯色菌株和91HE17菌株之间GroEL基因的一个425bp区域具有至少99.8%的序列同一性。分离株91HE17缺乏单克隆抗体6A1在恰菲埃立克体阿肯色菌株中鉴定出的一个表位。这种新的恰菲埃立克体分离株与阿肯色菌株非常相似，为证实感染人类的埃立克体之间存在多样性提供了机会。然后可以比较菌株之间不同的特定因素，以评估它们对细胞致病性以及最终对人类疾病发展的潜在贡献。
