[Amplification and restriction fragment length polymorphism analysis on the complete sequence of Sta56 gene of Orientia tsutsugamushi isolated from Shandong area].

Objective: To analyze the genetic differences of Orientia tsutsugamushi (Ot) Sta56 gene between Shandong isolates and other strains deposited in GenBank.

Methods: PCR and restriction fragment length polymorphism (RFLP) were used to amplify the complete sequence of Ot-Sta56 gene. RFLP profiles of Ot were predicted by a computer program according to their complete sequences of Ot-Sta56 gene. PCR amplicon from XDM2 strain was sequenced and analyzed by Clustal X (1.8) and PHYLIP software.

Results: The complete sequences (about 1.6 kbp) of Ot-Sta56 gene were amplified from B16 strain (isolated from patients), FXS2 strain (isolated from A. agrarius) and XDM2 strain. Four species of restriction endonucleases (Hha I, Hinf I, Hae III, Pst I) were used to digest the PCR amplicons from the 3 isolates. When comparing with the RFLP profiles of prototype Ot, the RFLP profiles of PCR amplicons from the 3 isolates were similar to those of Japan Kawasaki strain, but were quite different from the international reference strains Gilliam, Karp, Kato. Results from DNA sequence analysis showed that the complete sequence of Ot-Sta56 gene homology to Japan Kawasaki strain of XDM2 strain was 97%, and deduced amino acid sequence was 92%.

Conclusion: Data from the complete sequence of Sta56 gene indicated that the genotypes of Ot isolates in Shandong province were similar, but with distinction from the Kawasaki strain.