High Interlaboratory Reproducibility of Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry-Based Species Identification of Nonfermenting Bacteria

Abstract

Matrix-assisted laser desorption ionization-time of flight mass spectrometry has emerged as a rapid, cost-effective alternative for bacterial species identification. Identifying 60 blind-coded nonfermenting bacteria samples, this international study (using eight laboratories) achieved 98.75% interlaboratory reproducibility. Only 6 of the 480 samples were misidentified due to interchanges (4 samples) or contamination (1 sample) or not identified because of insufficient signal intensity (1 sample).Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has emerged as a fast and costeffective alternative for bacterial species identification in microbiology. On the basis of mass analysis of the protein composition of a bacterial cell, which is assumed to be characteristic for each bacterial species, it is possible to determine the species within few minutes, starting from whole cells, cell lysates, or crude bacterial extracts (2, 3, 5, 6). The proof of principle of MALDI-TOF MS for bacterial species identification was shown a decade ago (2, 5, 6); however, due to low reproducibility, it has not been widely adopted in clinical microbiology. We have recently shown that use of a larger mass range for detection (2,000 to 20,000 Da), dedicated analysis software for spectral pattern matching, and a highquality reference database of spectra generated from qualitycontrolled culture collection strains resulted in accurate species identifications, with high intralaboratory reproducibility (7). For interlaboratory reproducibility, there are only very limited data available (8, 10). We therefore evaluated the interlaboratory reproducibility for MALDI-TOF MS-based species identification in a multicenter study, applying the above-described MALDI-TOF MS improvements.(

High-throughput discrimination of bacteria isolated fromAstacus astacusandA. leptodactylus

“…Therefore, a reference database for MALDI-TOF MS based on the identification of non-fermenters was established (Mellmann et al, 2009;Campos Braga et al, 2013). MALDI-TOF MS was shown to identify correctly to the species level a number of Pseudomonads, and outperform 16S rRNA sequencing at identifying members of both Pseudomonas and Bacillus genera (Böhme et al, 2013).…”

Novel, Improved Sample Preparation for Rapid, Direct Identification from Positive Blood Cultures Using Matrix-Assisted Laser Desorption/Ionization Time-of-Flight (MALDI-TOF) Mass Spectrometry

“…For identification of bacterial colonies on agar plates, the MALDI Biotyper manufacturer recommends that score values be divided into three intervals; a log(score) of Ն2.0 is mainly considered to be the threshold for a match at the species level, a score of 1.7 to 2.0 indicates a close relationship (at least at the genus level), and a score of Ͻ1.7 indicates a non-reliable identification. 18,19 The applicability of these criteria for the direct identification of BC isolates was evaluated as part of the present study.…”

Phenotypical and Mass Spectral Assessment Methods for Identification of Some Contagious Mastitis Pathogens

“…These features are particularly attractive for bacterial isolates screening in contaminated milk at subclinical levels (Barreiro et al, 2010;El-Bouri et al, 2012). In addition, identification of bacteria by MALDI-TOF-MS has revealed prominent interlaboratory reproducibility (Mellmann et al, 2009) and is quickly being included as a routine method for animal and human laboratory microbiology. This technique requires slight Mass Spectral (MS) ability, the utilize of uncomplicated instruments and relatively fast operator training.…”