title: Direct bacterial identification in positive blood cultures by use of two commercial matrix-assisted laser desorption ionization-time of flight mass spectrometry systems.
abstract: Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) for the identification of bacteria and fungi was recently introduced in microbiology laboratories. This technology could greatly improve the clinical management of patients and guidance for chemotherapy. In this study, we used a commercial MALDI Sepsityper extraction method to evaluate the performance of two commercial MALDI-TOF MS systems, the Vitek MS IVD (bioMérieux) and the Microflex LT Biotyper (Bruker Daltonics) for direct bacterial identification in positive blood cultures. In 181 monomicrobial cultures, both systems generated genus to species level identifications for >90% of the specimens (Biotyper, 177/181 [97.8%]; Vitek MS IVD, 167/181 [92.3%]). Overall, the Biotyper system generated significantly more accurate identifications than the Vitek MS IVD system (P = 0.016; 177 versus 167 out of 181 specimens). The Biotyper system identified the minority species among polymicrobial blood cultures. We also compared the performance of an in-house extraction method with that of the Sepsityper on both MALDI-TOF MS systems. The in-house method generated more correct identifications at the genus level than the Sepsityper (96.7% versus 93.5%) on the Biotyper system, whereas the two methods exhibited the same performance level (88.0% versus 88.0%) on the Vitek MS IVD system. Our study confirmed the practical advantages of MALDI-TOF MS, and our in-house extraction method reduced the reagent cost to $1 per specimen, with a shorter turnaround time of 3 h, which is highly cost-effective for a diagnostic microbiology service.
authors.affiliation: Department of Microbiology, Queen Mary Hospital, The University of Hong Kong, Hong Kong Special Administrative Region, China.
authors.forename: Jonathan H K
authors.initials: JH
authors.lastname: Chen
authors.forename: Pak-Leung
authors.initials: PL
authors.lastname: Ho
authors.forename: Grace S W
authors.initials: GS
authors.lastname: Kwan
authors.forename: Kevin K K
authors.initials: KK
authors.lastname: She
authors.forename: Gilman K H
authors.initials: GK
authors.lastname: Siu
authors.forename: Vincent C C
authors.initials: VC
authors.lastname: Cheng
authors.forename: Kwok-Yung
authors.initials: KY
authors.lastname: Yuen
authors.forename: Wing-Cheong
authors.initials: WC
authors.lastname: Yam
mesh_terms: D016470:Bacteremia / Q000175:diagnosis* / Q000382:microbiology; D001419:Bacteria / Q000737:chemistry / Q000145:classification* / Q000302:isolation & purification*; D001431:Bacteriological Techniques / Q000191:economics / Q000379:methods*; D003365:Costs and Cost Analysis; D006801:Humans; D012680:Sensitivity and Specificity; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000191:economics / Q000379:methods*; D013997:Time Factors