Identification of Japanese isolates of spotted fever group rickettsiae

应用小鼠抗血清对从日本四国东南部患者中分离的斑点热群（SFG）立克次体进行了分析，以鉴定其种属。通过计算特异性差异（SPD），检测了5株日本分离株与致病性SFG立克次体标准株之间的抗原差异。每对日本菌株之间的SPD显示出它们的抗原同一性，而日本菌株与SFG的致病性标准菌株之间的SPD表明日本菌株与R.akari、R.australis、R.conorii、R.rickettsii和R. sibirica明显不同。研究还表明，日本菌株与泰国蜱斑疹伤寒立克次体（TT-118菌株）不同，泰国蜱斑疹伤寒立克次体分离自一种蜱，仅在东方已知。单克隆抗体分析日本株与标准株无交叉反应，但日本株与抗日本株单克隆抗体呈阳性反应。用抗日本株立克次体鼠抗血清进行Western免疫印迹，结果表明日本株立克次体与标准株立克次体完全不同。本研究中获得的结果表明，日本分离的SFG立克次体属于单一种，与已知对人类致病的任何SFG立克次体不同。我们建议将日本立克次体（Rickettsia japonica sp. nov.）命名为日本立克次体，因为它是在日本首次分离出来的。

Spotted fever group (SFG) rickettsiae isolated from patients in the southeastern part of Shikoku, Japan, were analyzed to identify the species by use of mouse antisera. Antigenic differences between five strains of Japanese isolates and standard strains of pathogenic SFG rickettsiae were examined by calculating the specificity difference (SPD). the SPD between each pair of Japanese strains showed their antigenic identity, while the SPD between Japanese strains and pathogenic standard strains of SFG indicated that Japanese strains are clearly distinct from R.akari, R.australis, R.conorii, R.rickettsii, and R.sibirica. It was also demonstrated that Japanese strains are different from Thai tick typhus rickettsia (strain TT-118) isolated from a tick, known only in the Orient. Monoclonal antibody analysis resulted in no cross-reaction between Japanese strain and standard strains but positive reactions of Japanese strains with monoclonal antibody to Japanese strain. Comparison of the Japanese strain and standard strains of SFG rickettsiae by Western immunoblotting with mouse antiserum to Japanese strain demonstrated that the Japanese strain are distinct from any of the standard strain of SFG rickettsiae. The results obtained in this study demonstrated that the Japanese isolates of SFG rickettsiae belong to a single species distinct from any SFG rickettsiae known to be pathogenic to humans. We proposed the taxonomic name Rickettsia japonica sp. nov. pertaining to Japan, since that is the country in which it was first isolated.