title: Optimization of the score cutoff value for routine identification of Staphylococcus species by matrix-assisted laser desorption ionization-time-of-flight mass spectrometry.
abstract: Staphylococcus species are important pathogens. We evaluated 2 score cutoffs (2.0 and 1.7) and the replicate number (a single or a duplicate test) on the identification of staphylococci using the Bruker matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS). A collection of 440 clinical isolates (11 species) and 144 reference strains (36 species) was evaluated. For clinical isolates using a cutoff of 2.0 and duplicate tests, the rates of species, genus, and unreliable identifications were 93.4%, 5.7%, and 0.9% respectively, while the respective values were 99.3%, 0.2%, and 0.5% when the cutoff was 1.7. The species identification rates were significantly higher (P<0.01) when a cutoff of 1.7 or a duplicate test was used. Similar results were obtained for reference strains. In conclusion, a cutoff of 1.7 and duplicate tests are recommended for identification of staphylococci using MALDI-TOF MS.
authors.affiliation: Institute of Biomedical Engineering, College of Engineering, National Cheng Kung University, Tainan, Taiwan.
authors.forename: Huan Wen
authors.initials: HW
authors.lastname: Han
authors.affiliation: Institute of Biomedical Engineering, College of Engineering, National Cheng Kung University, Tainan, Taiwan; Medical Device Innovation Center, National Cheng Kung University, Tainan, Taiwan.
authors.forename: Hsien Chang
authors.initials: HC
authors.lastname: Chang
authors.affiliation: Division of Clinical Microbiology, Department of Pathology, National Cheng Kung University Hospital, Tainan, Taiwan.
authors.forename: Ay Huei
authors.initials: AH
authors.lastname: Hunag
authors.affiliation: Department of Medical Laboratory Science and Biotechnology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
authors.forename: Tsung Chain
authors.initials: TC
authors.lastname: Chang
mesh_terms: D001431:Bacteriological Techniques / Q000379:methods*; D006801:Humans; D012680:Sensitivity and Specificity; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D013210:Staphylococcus / Q000737:chemistry* / Q000145:classification*
keywords: Coagulase-negative staphylococci; MALDI-TOF MS; Score values; Staphylococcus