710 - Non-invasive Diagnosis of Whipple Endocarditis Using Next-Generation Sequencing for Microbial Cell-free DNA in Plasma

Background: Tropheryma whipplei is a gram-positive bacillus that causes Whipple’s disease, a protean multisystemic syndrome classically characterized by arthralgias, chronic diarrhea, malabsorption, and weight loss. T. whipplei infection has a wide spectrum of clinical manifestations including pleuropulmonary disease, skin hyperpigmentation and cardiac infection. Endocarditis has been diagnosed in a small number of patients and may represent an atypical presentation of T. whipplei infection. Diagnosis can be challenging and has typically been accomplished with histopathology on resected valvular tissue or GI tract biopsy. Next-generation sequencing (NGS) of microbial cell-free DNA (mcfDNA) in plasma offers a rapid, non-invasive means of diagnosis of this rare cause of culture-negative endocarditis and challenging clinical entity.

Methods: McfDNA analysis was performed in a patient with culture negative endocarditis. McDNA was extracted from plasma and NGS was performed by Karius, Inc. (Redwood City, California). Human sequences were removed and remaining sequences were aligned to a curated database of over 1,400 pathogens. Organisms present above a predefined statistical significance threshold were reported and quantified in DNA molecules per microliter (MPM). Chart review was performed for clinical correlation.

Results: A 64 year-old male with history of valve replacement presented with significant deterioration of the mitral valve. An exhaustive infectious workup including blood cultures was negative. Karius testing detected T. whipplei at 766 MPM within two days of sample receipt. The normal range for T. whipplei is 0 MPM based on a cohort of 684 healthy individuals. Blood PCR for T. whipplei was confirmatory. Table 1: Clinical Parameters of Case


Conclusion: NGS for mcfDNA in plasma offers a rapid, non-invasive method for identifying T. whipplei and, to our knowledge, the first diagnosis of Whipple disease using NGS of plasma mcfDNA.