The Kawasaki strain was isolated from a febrile patient in Miyazaki Prefecture, on Kyushu in Japan in or before 1986 (Yamamoto et al., 1986). It was one of two similar isolates from a group of seven strains isolated as part of study of tsutsugamushi disease.
Immunological properties of the isolated Kawasaki strain were analyzed by indirect IF with hyperimmune guinea pig sera against the prototype and other isolated strains, including Gilliam, Karp, Kato and Kuroki. Kawasaki strain did not show clear crossreaction with any other strain.
Comparison of the polypeptide composition of Kawasaki strain with that of Gilliam, Karp, Kato, and Shimokoshi strains by PAGE revealed a similarity of the overall patterns. In immunoblotting tests, guinea pig polyclonal anti-Gilliam, anti-Karp, anti-Kato, and anti-Shimokoshi sera reacted clearly with the 54-56K polypeptide of the homologous strain. However, the 56K polypeptide in the Kawasaki strain was recognized only slightly if at all by these antisera, except anti-Gilliam serum which reacted moderately with the polypeptide. Nor was there any reaction of monoclonal anti-56K polypeptide antigens from any of these starins with proteins from the Kawasaki isolate.
The DNA sequence of the 56kDa TSA gene shows that, for at least this important antigenic gene, the Kawasaki strain represents a distinct well differentiated clade within O. tsutsugamushi. The genotype of the 56 kDA TSA gene of the Kawasaki strain currently represents about 24% of all sequences of this gene reported on the international DNA databases.
The Kawasaki serotype/genotype is now recognized as being present in Japan, Korea, China, Taiwan and India. It is either rare or absent in Southeast Asia (Thailand, Laos, Cambodia, Vietnam or Malaysia) and Australia.