Serological classification by monoclonal antibodies of Rickettsia tsutsugamushi isolated in Korea.

Antigenic types of 113 strains of Rickettsia tsutsugamushi isolated from Korean patients were analyzed by using murine polyclonal and monoclonal antibodies. The isolates can be classified in six groups according to their reaction to a panel of monoclonal antibodies. Nine isolates of group I were identified as the Gilliam serotype, and 13 isolates of groups II and III were identified as the Karp serotype. There were two groups that were considered to be a mixture of groups I and II or groups I and III, respectively. The remaining 88 strains of group IV had a unique antigenic determinant that was not present in the prototype strains (Karp, Kato, Gilliam), in addition to sharing common antigens with the prototype strains. Therefore these strains, which are more prevalent in Korea, seem to belong to a new serotype closely related to the Karp serotype.