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

TASAWAN SINGHSILARAK 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

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WATTANA LEOWATTANA 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

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SORNCHAI LOOAREESUWAN 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

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VAREE WONGCHOTIGUL 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

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JU JIANG 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

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ALLEN L. RICHARDS 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

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GEORGE WATT 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

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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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  • 10

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