Rickettsia japonica sp. nov., the Etiological Agent of Spotted Fever Group Rickettsiosis in Japan

Abstract

We propose the name Rickettsia japonica sp. nov. (with type strain YH [= ATCC VR-13631) for a serologically specific species of spotted fever group rickettsiae that are pathogenic for humans (J. Infect. Dis. 159:1122-1126, 1989; J. Clin. Microbiol. 28:1177-1180, 1990). The biologic and genomic characteristics of the organism (G+C content, 31.2 +-0.7 mol%) are essentially the same as those of other pathogenic spotted fever group rickettsiae, although the R. japonica isolates cause a persistent infection in Vero cells for many subcultures.In this paper we formally describe Rickettsia japonica (23,25), which has been identified as the causative agent of a human disease. The first isolate, strain YHT (T = type strain), was isolated in 1985 from the blood of a patient with febrile exanthematous illness in Japan by using a tissue culture technique (20). Five strains of the causative agent, including strain YHT, have been isolated from patients that were serodiagnosed as having a spotted fever group (SFG) rickettsiosis (22).Justification for a new species. The justification for establishing a new species for this organism is based on the current standard method for comparing rickettsial taxonomic types by serologic analysis (23). Experiments involving reciprocal cross-reactions of mouse polyclonal antibodies to strains of the new species and other species of SFG rickettsiae produced by the standard method were carried out to calculate the specificity differences. By using this approach we demonstrated that all five strains belong to a single species that is distinct from all of the previously described SFG rickettsiae that are known to be pathogenic for humans (23). In addition, none of the isolates reacted with mouse monoclonal antibodies that are species specific for other pathogenic SFG rickettsiae (23). Furthermore, the results of Western immunoblotting revealed different electrophoretic mobilities and antigenic reactivities for the major immunodominant high-molecular-weight surface polypeptides of the Japanese isolates and standard pathogenic SFG rickettsial strains (23). Species-specific monoclonal antibodies to R. japonica reacted only with strains of R. japonica, supporting the conclusion that R. japonica is a new species of SFG rickettsiae (25).

Seroepidemiologic survey of Orientia tsutsugamushi, Rickettsia typhi, and TT118 spotted fever group rickettsiae in rubber estate workers in Malaysia.

“…24 However, the investigators did not specify which rickettsial species was involved. 25 In Japan and Australia, less severe SFG rickettsiae appear to exist undetected for long periods (e.g., R. japonica and R. honei). 25,26 An unclassified tick-derived rickettsiae (TT118) of the spotted fever group 27 was used as antigen for the IIP test in our study.…”

“…25 In Japan and Australia, less severe SFG rickettsiae appear to exist undetected for long periods (e.g., R. japonica and R. honei). 25,26 An unclassified tick-derived rickettsiae (TT118) of the spotted fever group 27 was used as antigen for the IIP test in our study. However, it may not be the most appropriate antigen for serodiagnosis if antigenic variation exists in the local isolates of spotted fever group rickettsiae.…”

Tick- and flea-borne rickettsial emerging zoonoses

“…Between 1984 and 2004, nine more species or subspecies of tick-borne spotted fever rickettsiae were identified as emerging pathogens throughout the world, including, R. japonica in Japan [6,46,65,71,72,[82][83][84]146]; "R. conorii caspia" in Astrakhan [35,38,39,143], Africa [47] and Kosovo [48]; R. africae in sub-Saharan Africa and the West Indies [62,63]; R. honei in the Flinders Island, offshore of Australia [9,57,140,141], the Island of Tasmania, Australia [153], Thailand [73], and possibly in the USA [13]; R. slovaca in Europe [29,74,101,122]; "R. sibirica mongolotimonae" in China [157], Europe [44,118] and Africa [106,113]; R. heilongjiangensis in China [42,49]; R. aeschlimannii in Africa [11,112,121] and Europe [43]; and finally R. parkeri in the USA [104]. R. helvetica is also suspected to be a human pathogen in Europe [45] and Asia [46,61,107], but this needs c...…”

Cross‐Reactivity of Rickettsia japonica and Rickettsia typhi Demonstrated by Immunofluorescence and Western Immunoblotting

“…Rickettsia japonica, a causative agent of Oriental spotted fever (OSF) encountered in Japan, was a newly identified species of spotted fever group (SFG) rickettsia (23,26,27,29). The organisms were isolated from patients in the Muroto area located in the southeastern part of Shikoku, one of the four main islands of Japan (23)(24)(25).…”