Assessment of a quantitative multiplex 5’ nuclease real-time PCR for spotted fever and typhus group rickettsioses and Orientia tsutsugamushi

Abstract

Department of Pathology,The Johns Hopkins University School of Medicine, Baltimore, MD, USAINTRODUCTIONScrub typhus, murine typhus and spotted fevergroup rickettsioses are re-emerging causes ofacute febrile illness in south and southeast Asia[1,2], whereas spotted fever group and typhusgroup rickettsioses are globally distributed. Datafrom the United States suggest both increasingincidence and serious under-reporting (fewerthan a quarter of cases) [3]. Lack of accurate,rapid diagnostic tools has limited assessment ofthe global burden, distribution and clinical fea-tures of rickettsioses, including the pathogenicityof different species [4]. Paired sera, the currentgold standard, at best informs epidemiology,because diagnoses can be made in retrospect onlyif clinical suspicion, follow-up and laboratoryinfrastructure enable a convalescent blood sampleto be obtained and tested [5]. Serology also doesnot reliably distinguish among species. Becauserickettsial illnesses clinically mimic other causesof undifferentiated fever that require differenttreatment, better diagnostic tools are needed toguide management and avert needless morbidityand mortality [1,2]. To address this need, wesought to develop a quantitative, multiplex5¢-nuclease real-time PCR assay to diagnosespotted fever (SFGR) and typhus group (TGR)rickettsioses, as well as Orientia tsutsugamushi(OT), the cause of scrub typhus.METHODS