title: Identification of pathogenic microorganisms directly from positive blood vials by matrix-assisted laser desorption/ionization time of flight mass spectrometry.
abstract: Matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) is a promising and fast method for identifying fungi and bacteria directly from positive blood cultures. Various pre-treatment methods for MALDI-TOF MS identification have been reported for this purpose. In-house results for identification of bacterial colonies by MALDI-TOF MS using a cut-off score of 1.5 did not reduce the diagnostic accuracy compared with the recommended cut-off score of 1.8. A 3-month consecutive study of positive blood cultures was carried out in our laboratory to evaluate whether the Sepsityper™ Kit (Bruker Daltonics) with Biotyper 2.0 software could be used as a fast diagnostic tool for bacteria and fungi and whether a 1.5 cut-off score could improve species identification compared with the recommended score of 1.8. Two hundred and fifty-six positive blood vials from 210 patients and 19 blood vials spiked with fungi were examined. Using the cut-off score of 1.8, 81% Gram-negative bacteria were identified to the species level compared to 84% using a cut-off score of 1.5. For Gram-positive bacteria 44% were identified to the species level with a cut-off of 1.8 compared to 55% with the value of 1.5. The overall identification rate was 63% (cut-off 1.5) and 54% (cut-off 1.8). Seventy-seven per cent of fungal species were identified with both log scores. MALDI-TOF MS was in this study found to be a powerful tool in fast diagnosis of Gram-negative bacteria and fungi and to a lesser degree of Gram positives. Using 1.5 as cut-off score increased the diagnosis for both Gram-positives and -negatives bacteria.
authors: Department of Clinical Microbiology, Rigshospitalet, University Hospital of Copenhagen.
authors: Bettina
authors: B
authors: Nonnemann
authors: Michael
authors: M
authors: Tvede
authors: Thomas
authors: T
authors: Bjarnsholt
mesh_terms: D016470:Bacteremia / Q000175:diagnosis* / Q000382:microbiology; D001424:Bacterial Infections / Q000175:diagnosis* / Q000382:microbiology; D016469:Fungemia / Q000175:diagnosis / Q000382:microbiology; D005658:Fungi / Q000302:isolation & purification*; D006090:Gram-Negative Bacteria / Q000302:isolation & purification*; D006094:Gram-Positive Bacteria / Q000302:isolation & purification*; D006801:Humans; D009181:Mycoses / Q000175:diagnosis* / Q000382:microbiology; D011933:Reagent Kits, Diagnostic; D012680:Sensitivity and Specificity; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D011933:Reagent Kits, Diagnostic
keywords: Matrix-assisted laser desorption/ionization time of flight mass spectrometry; blood culture