2-STEP POLYMERASE CHAIN-REACTION FOR DIAGNOSIS OF SCRUB TYPHUS AND IDENTIFICATION OF ANTIGENIC VARIANTS OF RICKETTSIA-TSUTSUGAMUSHI

Two-step polymerase chain reaction (nested PCR) method was examined fo r the diagnosis of scrub typhus. Primers were derived from the type-sp ecific antigen (TSA) gene DNA sequences of Rickettsia tsutsugamushi, G illiam strain. These primers served to produce rickettsia-specific pro ducts in the amplification of template DNA prepared from all serovaria nts, Gilliam, Karp, Kato, Kawasaki, Kuroki and Shimokoshi strains, and the fragments of product after digestion with several kinds of restri ction endonuclease showed the respective patterns to strain in acrylam ide or agarose gel electrophoresis. The rickettsia-specific DNAs were also derived, by this nested PCR, by amplifying DNA from patients' blo ods and mites from endemic areas, and the serotype of rickettsiae infe cted to these hosts could be identified from fragment patterns of the amplified products observed after endonuclease treatment. These result s indicate that this PCR is sensitive and specific method not only for detection of rickettsial DNA in patient specimens and in mites, but a lso for the typing of rickettsiae infected to these hosts.