Identification of Orientia tsutsugamushi, spotted fever group and typhus group Rickettsia by duplex and nested PCR methods

To identify members of genera of rickettsia and O. tsutsugamushi simultaneously. Methods: Rapid and duplex and nested PCR methods have been established by designing primers based on the conserved regions of heat shock protein GroEL gene. 345 mouse viscera samples including liver, spleen and kidney, 96 Xenopsylla cheopis and 32 chiggers collected from Hongta areas of Yuxi city, Yunnan province were tested by the new PCR methods. Results: The result of the study showed that the new PCR methods could identify most members of genera. -Rickettsia and Orientia simultaneously with 100% one copy per microliter. The results of detection prevalence of rickettsioses in mouse, flea and mites DNA samples showed that the total rickettsia infection rate in mouse was 34.78% (120/345). The total infection rates in R. typhi, O. t Karp and R. sibirica of mouse samples were 28.12% (97/345), 19.71% (68/345) and 0.29% (1/345) respectively. Co-infection rates in R. typhi and O. t Karp of mouse samples were 13.33% (46/345). O. t Karp type has been the main epidemic strain in these areas. Conclusion: We concluded that this PCR method could be used to detect multi-genera rickettsia simultaneously. Molecular evidences provided in this and previous studies strongly support that Hongta areas of Yuxi city are a natural focus for typhus and scrub typhus with the common occurrence of their confection.