49. Rapid Detection and Identification of Tick-Borne Pathogens Directly from Blood using PCR and Electrospray Ionization Mass Spectrometry
Poster: Mon 2:00-3:00PM
Mark Eshoo
Ibis Biosciences
Mark W. Eshoo1, Chris D. Crowder1, Haijing Li2, Heather E. Matthews1, Shufang Meng2,
Susan E. Sefers2, Charles W. Stratton2, 3, David J. Ecker1, and Yi-Wei Tang2, 3, *

1Ibis Biosciences, a subsidiary of Abbott Molecular, Inc., Carlsbad, CA 92008;
Departments of Pathology2 and Medicine3, Vanderbilt University School of Medicine, Nashville, TN 37232
The potential for fatal outcome from tick-borne human infections such as ehrlichiosis emphasizes the need for rapid diagnosis. We developed and validated an Ibis T5000 assay (Ibis Biosciences, Inc., Carlsbad, CA) that can detect and identify a wide range of tick-borne pathogens. This multi-locus assay employs 16 broad-range PCR primer pairs targeting all known tick-borne pathogen families. Electrospray ionization mass spectrometry of the PCR amplicons was used to determine their base composition. These base composition signatures were subsequently used to identify the organisms found in the samples. The assay was developed using field collected ticks and has been shown to be sensitive to the stochastic limits of PCR. Whole blood (198), cerebrospinal fluid (20) and plasma (1) samples, which were originally submitted for Ehrlichia species detection by a colorimetric microtiter plate PCR (PCR-EIA), were collected consecutively from January 5 to August 1, 2008 at Vanderbilt University Hospital. Among the total 219 specimens, PCR-EIA detected 40 Ehrlichia species with a positive rate of 18.3%. The Ibis system detected Ehrlichia in 38 of the 40 PCR-EIA-positive samples and 1 in 179 of the PCR-EIA-negative specimens, giving sensitivity and specificity of 95.0% and 99.4%, respectively. The 38 Ehrlichia-dual positive specimens were further characterized by the Ibis system to the species level (E. cheffeensis, 35; E. ewingii, 3) with a 100% agreement to that identified by PCR-EIA using additional species-specific probes. In addition, the Ibis system detected 3 Rickettsi rickettsii positive specimens, which were confirmed by serology and clinical findings. The Ibis T5000 system, which can be completed within five hours from specimen processing to result reporting, provides rapid and accurate detection and identification of a broad range of pathogens causing tick-borne human infections.