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DETECTION OF ORIENTIA TSUTSUGAMUSHI IN CLINICAL SAMPLES BY QUANTITATIVE REAL-TIME POLYMERASE CHAIN REACTION

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  • 1 Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand; Department of Microbiology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand; Rickettsial Diseases Department, Naval Medical Research Center, Silver Spring, Maryland; Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand and Department of Medicine, Hawaii AIDS Clinical Research Program, University of Hawaii, Manoa, Honolulu, Hawaii

Orientia tsutsugamushi infection causes scrub typhus, a common zoonosis of rural Asia. Orientia tsutsugamushi was recently detected by a real-time quantitative polymerase chain reaction (qPCR) assay in animal specimens. We evaluated the same qPCR assay in specimens obtained from patients with serologically proven scrub typhus infections. The 47-kDa qPCR assay was more sensitive than was mouse inoculation; it was reactive in whole blood specimens from all 10 isolate-positive patients and in 7 of 17 isolate-negative individuals (P = 0.003, Fisher’s two-tailed exact test). As few as 1,076 O. tsutsugamushi copies/μL were detected in whole blood. Four of 7 sera from isolate-proven scrub typhus infections were also reactive by qPCR. The assay was unreactive in all 12 individuals without scrub typhus infection. This is the first demonstration of a sensitive and specific real-time qPCR assay for human scrub typhus infection.

Author Notes

Reprint requests: George Watt, Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand 10400.
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