title: Detection and identification of Ehrlichia species in blood by use of PCR and electrospray ionization mass spectrometry.
abstract: Rapid detection and identification of Ehrlichia species improves clinical outcome for patients suspected of ehrlichiosis. We describe an assay that employs multilocus PCR and electrospray ionization mass spectrometry (PCR/ESI-MS) to detect and identify Ehrlichia species directly from blood specimens. The results were compared to those of a colorimetric microtiter PCR enzyme immunoassay (PCR-EIA) used as a diagnostic assay. Among 213 whole-blood samples collected from patients who were clinically suspected of ehrlichiosis from 1 May to 1 August 2008 at Vanderbilt University Hospital, 40 were positive for an Ehrlichia species by PCR/ESI-MS, giving a positive rate of 18.8%. In comparison to the PCR-EIA, PCR/ESI-MS possessed a sensitivity, a 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 the 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 that 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 6 h, 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.
authors: Ibis Biosciences, Carlsbad, California 92008, USA.
authors: Mark W
authors: MW
authors: Eshoo
authors: Chris D
authors: CD
authors: Crowder
authors: Haijing
authors: H
authors: Li
authors: Heather E
authors: HE
authors: Matthews
authors: Shufang
authors: S
authors: Meng
authors: Susan E
authors: SE
authors: Sefers
authors: Rangarajan
authors: R
authors: Sampath
authors: Charles W
authors: CW
authors: Stratton
authors: Lawrence B
authors: LB
authors: Blyn
authors: David J
authors: DJ
authors: Ecker
authors: Yi-Wei
authors: YW
authors: Tang
mesh_terms: D016470:Bacteremia / Q000175:diagnosis* / Q000382:microbiology; D001431:Bacteriological Techniques / Q000379:methods*; D001769:Blood / Q000382:microbiology*; D004536:Ehrlichia / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification*; D016873:Ehrlichiosis / Q000175:diagnosis* / Q000382:microbiology; D006801:Humans; D009345:Neisseria meningitidis / Q000302:isolation & purification; D016133:Polymerase Chain Reaction / Q000379:methods*; D011237:Predictive Value of Tests; D011550:Pseudomonas aeruginosa / Q000302:isolation & purification; D012284:Rickettsia rickettsii / Q000302:isolation & purification; D012680:Sensitivity and Specificity; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D013211:Staphylococcus aureus / Q000302:isolation & purification; D013997:Time Factors