Detection and Identification of Ehrlichia species in Blood

Rapid detection and identification of Ehrlichia species improves clinical
outcome in patients suspected of ehrlichiosis. We describe an assay that employs
multi-locus PCR and electrospray mass spectrometry (PCR/ESI-MS) to detect and
identify Ehrlichia species directly from blood specimens. The results were
compared to a colorimetric microtiter PCR (PCR-EIA) being used as a diagnostic
assay. Among 213 whole blood samples collected from patients who were clinically
suspected of ehrlichiosis from May 1 to August 1, 2008 at Vanderbilt University
Hospital, 40 were positive for an Ehrlichia species by the PCR/ESI-MS, giving a
positive rate of 18.8%. In comparison to the PCR-EIA, the PCR/ESI-MS possessed
sensitivity, specificity and positive and negative predictive values of 95.0%,
98.8%, 95.0%, and 98.8%, respectively. The 38 specimens that were positive for
Ehrlichia by both PCR/ESI-MS and PCR-EIA were further characterized to the
species level with 100% agreement between the two assays. In addition,
Rickettsia rickettsii was detected by PCR/ESI-MS from four specimens which were
confirmed retrospectively by serology and PCR-EIA. In three specimens, the
PCR/ESI-MS assay identified Pseudomonas aeruginosa, Neisseria meningitidis, and
Staphylococcus aureus; these were confirmed by culture and/or clinical diagnosis
as being clinically relevant. From specimen processing to result reporting, the
PCR/ESI-MS assay can be completed within six hours, providing another laboratory
tool for the diagnosis of ehrlichiosis. Moreover, this system may provide rapid
detection and identification of additional pathogens directly from blood
specimens.
J Clin Microbiol. 2009 Dec 2; [Epub ahead of print]

Detection and Identification of Ehrlichia species in Blood Using PCR and
Electrospray Ionization Mass Spectrometry.

Eshoo MW, Crowder CD, Li H, Matthews HE, Meng S, Sefers SE, Sampath R, Stratton
CW, Blyn LB, Ecker DJ, Tang YW.

Ibis Biosciences, a subsidiary of Abbott Molecular, Inc., Carlsbad, CA 92008;
Departments of Pathology, and Medicine, Vanderbilt University School of
Medicine, Nashville, TN 37232.