title: High-throughput identification of bacteria and yeast by matrix-assisted laser desorption ionization-time of flight mass spectrometry in conventional medical microbiology laboratories.
abstract: Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) is suitable for high-throughput and rapid diagnostics at low costs and can be considered an alternative for conventional biochemical and molecular identification systems in a conventional microbiological laboratory. First, we evaluated MALDI-TOF MS using 327 clinical isolates previously cultured from patient materials and identified by conventional techniques (Vitek-II, API, and biochemical tests). Discrepancies were analyzed by molecular analysis of the 16S genes. Of 327 isolates, 95.1% were identified correctly to genus level, and 85.6% were identified to species level by MALDI-TOF MS. Second, we performed a prospective validation study, including 980 clinical isolates of bacteria and yeasts. Overall performance of MALDI-TOF MS was significantly better than conventional biochemical systems for correct species identification (92.2% and 83.1%, respectively) and produced fewer incorrect genus identifications (0.1% and 1.6%, respectively). Correct species identification by MALDI-TOF MS was observed in 97.7% of Enterobacteriaceae, 92% of nonfermentative Gram-negative bacteria, 94.3% of staphylococci, 84.8% of streptococci, 84% of a miscellaneous group (mainly Haemophilus, Actinobacillus, Cardiobacterium, Eikenella, and Kingella [HACEK]), and 85.2% of yeasts. MALDI-TOF MS had significantly better performance than conventional methods for species identification of staphylococci and genus identification of bacteria belonging to HACEK group. Misidentifications by MALDI-TOF MS were clearly associated with an absence of sufficient spectra from suitable reference strains in the MALDI-TOF MS database. We conclude that MALDI-TOF MS can be implemented easily for routine identification of bacteria (except for pneumococci and viridans streptococci) and yeasts in a medical microbiological laboratory.
authors.affiliation: Department of Medical Microbiology, Leiden University Medical Center, Leiden, Netherlands. s.q.van_veen@lumc.nl
authors.forename: S Q
authors.initials: SQ
authors.lastname: van Veen
authors.forename: E C J
authors.initials: EC
authors.lastname: Claas
authors.forename: Ed J
authors.initials: EJ
authors.lastname: Kuijper
mesh_terms: D001419:Bacteria / Q000737:chemistry / Q000145:classification / Q000302:isolation & purification*; D001424:Bacterial Infections / Q000175:diagnosis* / Q000382:microbiology; D019411:Clinical Laboratory Techniques / Q000379:methods*; D005658:Fungi / Q000737:chemistry / Q000145:classification / Q000302:isolation & purification*; D006801:Humans; D009181:Mycoses / Q000175:diagnosis* / Q000382:microbiology; D012680:Sensitivity and Specificity; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*