On Rickettsia Nomenclature

his issue of Emerging Infectious Diseases contains 2 independent reports of Rickettsia sibirica infections in Spain and Portugal. The authors identify the agent both as a subspecies (1) and as a strain (2). This inconsistency refl ects a lack of consensus regarding the use of subspe-cies designations for Rickettsia taxa, so appropriate designation of these pathogens as strains or subspecies remains problematic. Tick-borne typhus of northern Asia (or North Asian spotted fever) was fi rst discovered in the 1930s, and its eti-ologic agent, R. sibirica, was formally described in 1949. In 1993, an isolate designated " mongolitimonae " was fi rst discovered in the People's Republic of China (3), considered a new species (4), and fi nally described as a new genotype of R. sibirica (5). A proposal to create 2 subspecies, R. sibirica sibirica and R. sibirica mongolitimonae, was recently published (6). A new prokaryote name must be both effectively and validly published. To become effectively published, a name must meet certain rules, as defi ned by the International Code of Nomenclature of Bacteria (7). To become validly published, the name must then appear on a Validation List published in the International Journal of Systematic and Evolutionary Microbiology (8). This provides an orderly system for bacterial names to be properly introduced and published in the scientifi c literature. Valid and nonvalid names are listed on regularly updated websites (9,10). Names introduced without being validated have no standing in bacterial nomenclature. That is currently the status of these proposed R. sibirica subspecies. Therefore, the use of strain designations is still appropriate. If, and when, the subspecies names are validated, they are likely to be adopted and routinely used in the literature. Rickettsial taxonomy continues to evolve, and future changes should be determined by critical scientifi c judgments and general consensus within the scientifi c community. Control and Prevention. His research interests include laboratory and epidemiologic investigations targeting the detection, prevention , and control of rickettsial and Bartonella spp. diseases and Q fever. identifi cation of two new strains of spotted fever group rickettsiae isolated from China. sequence-based criteria for identifi cation of new Rickettsia isolates and description of Rickettsia heilongjiangensis sp. nov.