Assessment of Reproducibility of Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry for Bacterial and Yeast Identification

Abstract

Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry (MS) has revolutionized the identification of clinical bacterial and yeast isolates. However, data describing the reproducibility of MALDI-TOF MS for microbial identification are scarce. In this study, we show that MALDI-TOF MS-based microbial identification is highly reproducible and can tolerate numerous variables, including differences in testing environments, instruments, operators, reagent lots, and sample positioning patterns. Finally, we reveal that samples of bacterial and yeast isolates prepared for MALDI-TOF MS identification can be repeatedly analyzed without compromising organism identification. Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry (MS) has revolutionized the identification of microorganisms in the clinical microbiology laboratory, and numerous studies have documented the superior analytical performance characteristics of MALDI-TOF MS compared to those of manual and automated biochemical methods for microorganism identification (1-4). Compared to biochemicalbased identification, MALDI-TOF MS-based identification significantly reduces the cost and time to microbial identification while simultaneously enhancing favorable patient outcomes and reducing the cost and length of hospitalization (5-8).Despite the implementation of MALDI-TOF MS in clinical microbiology laboratories, studies specifically designed to assess the reproducibility of MALDI-TOF MS platforms for microorganism identification are limited. As part of a multicenter study, using the manufacturer's default unmodified settings, we assessed the ability of a MALDI-TOF MS platform, the Vitek MS version 2.0 system (bioMérieux, Durham, NC, USA), to reproducibly identify bacterial and yeast isolates at three different sites. We probed variations in operators, reagent lots, and sample positioning patterns. Finally, the reproducibility of microbial identification after initial analysis (initial read) of the samples compared to repeat analysis (reread) of the same samples was investigated. The rereading of samples may be of importance in instances when the definition of additional microbiological characteristics is required, e.g., in the detection of antimicrobial resistance determinants, or when the initial read failed due to operator or instrument error.Over five different days, reproducibility studies were performed with three independent Vitek MS version 2.0 systems located at three geographically distinct sites in the United States: site 1 was in Missouri, site 2 was in New York, and site 3 was in California. At each site, two different operators conducted reproducibility testing. All isolates were applied to target slides (bioMérieux) using disposable loops (Sarstedt, Newton, NC, USA). For bacterial isolates, 1 l of matrix solution (␣-cyano-4-hydroxycinnamic acid; bioMérieux) was overlaid and allowed to dry at room temperature before analysis. Prior to the application of 1 l of matrix solution, yeast isola...

Clinical Performance of a Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry Method for Detection of Certain bla KPC -Containing Plasmids

“…It is possible that use-dependent wear of integral instrument parts (e.g., lasers and turbo pumps) over time may not have significant consequences for routine bacterial and yeast identification, where many redundant spectral features are calculated into the overall identification algorithm. Reproducibility of MALDI-TOF MS for bacterial and yeast identification has been well demonstrated (17)(18)(19), leading to recent FDA approval of bacterial and yeast databases for the Bruker BioTyper and Vitek MS (bioMérieux, Durham, NC). In our case, declining instrument performance was not obvious from our routine bacterial runs; rather, instrument compromise was suspected when identification scores from our routine clinical mold and mycobacterial runs decreased over time.…”

Impact of investigational microbiota therapeutic RBX2660 on the gut microbiome and resistome revealed by a placebo-controlled clinical trial

“…The remaining fecal samples were stored frozen at -80˚C until metagenomic DNA extraction. Isolate colonies were sub-cultured to trypticase soy agar with 5% sheep blood (Becton Dickinson, Franklin Lakes, NJ) and identi ed using VITEK MS matrix-assisted laser desorption/ionization time-of-ight mass spectrometry (MALDI-TOF MS) system [64,65]. Each isolate was frozen in tryptic soy broth with glycerol at -80˚C.…”

MALDI-TOF Mass Spectrometry for Microorganism Identification

“…Moreover, manufacturers regularly update databases, making it challenging to compare inter-study performance even within the same system. Nevertheless, MALDI-TOF MS is highly reproducible when performed across multiple laboratories using the same MS system with the same identification database (Westblade et al, 2015).…”