Isolation of oriential tsutsugamushi and sequence analysis on it's 56kD protein gene of scrub typhus

  Objective   To isolate orientia Tsutsugamushi(Ot)from patients, host animal(Rodents)and vector mite (trombiculid mite)on Pingtan island and analyze the gene of Ot DNA for the purpose of prevention.

  Methods   The mice were peritoneal injected by untreated patient's blood, spleen of rodent and leptotrombidium(L.)Deliense respectively and the Ot were observed from infected mice on the microscope.Then the 1 350 bp DNA fragment encoding the Ot 56kD protein can be amplified after Ot DNA being extracted from spleen of the infected mice.The specific genes were sequenced and compared with those of standard strains karp, kato, Gilliam, kawasaki and Kuroki for their homology analysis.

  Results   Three Ot strains were isolated from patient, host rodent and vector mite respectively.The typical Ot can be seen in the cytoplasm of infected cell on the microscope.About 1 350 bp DNA fragments of 56kD protein were amplified and sequenced.The three isolates were almost identical to each other(with nucleotide sequence homology > 99.5%).Compared with Karp, kato, Gilliam, Kawasaki, Kuroki, their gene sequence homology of 56kD protein were 93.8%, 66.2%, 85.1%, 69.6%, 84.2% respectively.

  Conclusion   This was the first report of scrub typhus in the season of spring and also firstly identifying the Ot by molecular technique on Pingtan island.The Ot strains here were highly homologous to Karp type.