[Molecular typing of Taiwanese Orientia tsutsugamushi isolates by restriction fragment profile]

Scrub typhus, which is caused by Orientia tsutsugamushi, is one of the reportable diseases in Taiwan, ROC. Positive cases seemed to be increasing in recent years and our laboratory had confirmed a total of 247 cases in 1997. In this study, 71 strains of O. tsutsugamushi were isolated from heparinized blood of the patients by cell culture, and their DNA was isolated. Two-step polymerase chain reaction was then used to amplify a specific sequence from the DNA, which was digested with restriction enzymes, Hha I and Sfa NI, for typing. With this technique, 34 strains gave rise to the same profile as that of the Kuroki type, 6 as the Karp type and 2 as the Gilliam type. The remaining 28 strains produced fragment profiles different from those of types Karp, Kato, Kawasaki, Kuroki, Gilliam and Shimokoshi and, therefore, were classified as 6 new types designated Taiwan A to Taiwan F, respectively. These strains with profiles different from those of the standard Japanese strains may represent the local mutant strains.