g Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF) is gaining momentum as a tool for bacterial identification in the clinical microbiology laboratory. Compared with conventional methods, this technology can more readily and conveniently identify a wide range of organisms. Here, we report the findings from a multicenter study to evaluate the Vitek MS v2.0 system (bioMérieux, Inc.) for the identification of aerobic Gram-positive bacteria. A total of 1,146 unique isolates, representing 13 genera and 42 species, were analyzed, and results were compared to those obtained by nucleic acid sequence-based identification as the reference method. For 1,063 of 1,146 isolates (92.8%), the Vitek MS provided a single identification that was accurate to the species level. For an additional 31 isolates (2.7%), multiple possible identifications were provided, all correct at the genus level. Mixed-genus or single-choice incorrect identifications were provided for 18 isolates (1.6%). Although no identification was obtained for 33 isolates (2.9%), there was no specific bacterial species for which the Vitek MS consistently failed to provide identification. In a subset of 463 isolates representing commonly encountered important pathogens, 95% were accurately identified to the species level and there were no misidentifications. Also, in all but one instance, the Vitek MS correctly differentiated Streptococcus pneumoniae from other viridans group streptococci. The findings demonstrate that the Vitek MS system is highly accurate for the identification of Gram-positive aerobic bacteria in the clinical laboratory setting.

The optimal management of fungal infections is correlated with timely organism identification. Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry (MS) is revolutionizing the identification of yeasts isolated from clinical specimens. We present a multicenter study assessing the performance of the Vitek MS system (bioMérieux) in identifying medically important yeasts. A collection of 852 isolates was tested, including 20 Candida species (626 isolates, including 58 C. albicans, 62 C. glabrata, and 53 C. krusei isolates), 35 Cryptococcus neoformans isolates, and 191 other clinically relevant yeast isolates; in total, 31 different species were evaluated. Isolates were directly applied to a target plate, followed by a formic acid overlay. Mass spectra were acquired using the Vitek MS system and were analyzed using the Vitek MS v2.0 database. The gold standard for identification was sequence analysis of the D2 region of the 26S rRNA gene. In total, 823 isolates (96.6%) were identified to the genus level and 819 isolates (96.1%) were identified to the species level. Twenty-four isolates (2.8%) were not identified, and five isolates (0.6%) were misidentified. Misidentified isolates included one isolate of C. albicans (n ‫؍‬ 58) identified as Candida dubliniensis, one isolate of Candida parapsilosis (n ‫؍‬ 73) identified as Candida pelliculosa, and three isolates of Geotrichum klebahnii (n ‫؍‬ 6) identified as Geotrichum candidum. The identification of clinically relevant yeasts using MS is superior to the phenotypic identification systems currently employed in clinical microbiology laboratories.

Accurate and timely identification of anaerobic bacteria is critical to successful treatment. Classic phenotypic methods for identification require long turnaround times and can exhibit poor species level identification. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) is an identification method that can provide rapid identification of anaerobes. We present a multi-centre study assessing the clinical performance of the VITEK(®) MS in the identification of anaerobic bacteria. Five different test sites analysed a collection of 651 unique anaerobic isolates comprising 11 different genera. Multiple species were included for several of the genera. Briefly, anaerobic isolates were applied directly to a well of a target plate. Matrix solution (α-cyano-4-hydroxycinnamic acid) was added and allowed to dry. Mass spectra results were generated with the VITEK(®) MS, and the comparative spectral analysis and organism identification were determined using the VITEK(®) MS database 2.0. Results were confirmed by 16S rRNA gene sequencing. Of the 651 isolates analysed, 91.2% (594/651) exhibited the correct species identification. An additional eight isolates were correctly identified to genus level, raising the rate of identification to 92.5%. Genus-level identification consisted of Actinomyces, Bacteroides and Prevotella species. Fusobacterium nucleatum, Actinomyces neuii and Bacteroides uniformis were notable for an increased percentage of no-identification results compared with the other anaerobes tested. VITEK(®) MS identification of clinically relevant anaerobes is highly accurate and represents a dramatic improvement over other phenotypic methods in accuracy and turnaround time.

This multicenter study evaluated the accuracy of matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry identifications from the VITEK MS system (bioMérieux, Marcy l'Etoile, France) for Enterobacteriaceae typically encountered in the clinical laboratory. Enterobacteriaceae isolates (n = 965) representing 17 genera and 40 species were analyzed on the VITEK MS system (database v2.0), in accordance with the manufacturer's instructions. Colony growth (≤72 h) was applied directly to the target slide. Matrix solution (α-cyano-4-hydroxycinnamic acid) was added and allowed to dry before mass spectrometry analysis. On the basis of the confidence level, the VITEK MS system provided a species, genus only, or no identification for each isolate. The accuracy of the mass spectrometric identification was compared to 16S rRNA gene sequencing performed at MIDI Labs (Newark, DE). Supplemental phenotypic testing was performed at bioMérieux when necessary. The VITEK MS result agreed with the reference method identification for 96.7% of the 965 isolates tested, with 83.8% correct to the species level and 12.8% limited to a genus-level identification. There was no identification for 1.7% of the isolates. The VITEK MS system misidentified 7 isolates (0.7 %) as different genera. Three Pantoea agglomerans isolates were misidentified as Enterobacter spp. and single isolates of Enterobacter cancerogenus, Escherichia hermannii, Hafnia alvei, and Raoultella ornithinolytica were misidentified as Klebsiella oxytoca, Citrobacter koseri, Obesumbacterium proteus, and Enterobacter aerogenes, respectively. Eight isolates (0.8 %) were misidentified as a different species in the correct genus. The VITEK MS system provides reliable mass spectrometric identifications for Enterobacteriaceae.

Studies have demonstrated that matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) is a rapid, accurate method for the identification of clinically relevant bacteria. The purpose of this study was to evaluate the performance of the VITEK MS v2.0 system (bioMérieux) for the identification of the non-Enterobacteriaceae Gram-negative bacilli (NEGNB). This multi-center study tested 558 unique NEGNB clinical isolates, representing 18 genera and 33 species. Results obtained with the VITEK MS v2.0 were compared with reference 16S rRNA gene sequencing and when indicated recA sequencing and phenotypic analysis. VITEK MS v2.0 provided an identification for 92.5 % of the NEGNB isolates (516 out of 558). VITEK MS v2.0 correctly identified 90.9 % of NEGNB (507 out of 558), 77.8 % to species level and 13.1 % to genus level with multiple species. There were four isolates (0.7 %) incorrectly identified to genus level and five isolates (0.9 %), with one incorrect identification to species level. The remaining 42 isolates (7.5 %) were either reported as no identification (5.0 %) or called "mixed genera" (2.5 %) since two or more different genera were identified as possible identifications for the test organism. These findings demonstrate that the VITEK MS v2.0 system provides accurate results for the identification of a challenging and diverse group of Gram-negative bacteria.

We report the clinical and analytical performance of an isothermal thermophilic helicase-dependent amplification assay for blood Plasmodium parasite detection and species-level identification. The assay amplifies the 18S rRNA gene fragment of all Plasmodium species and uses a species-specific probe and a pan-malarial probe to definitively identify Plasmodium falciparum from other infectious Plasmodium species. Amplicon-probe hybridization products are detected with a disposable dipstick enclosed in a cassette. With a pan-malarial-positive and P. falciparum-negative result, an additional test is performed to detect if the pan-malarial-positive band was the result of the presence of Plasmodium vivax. The assay uses only 2 μL of human whole blood directly for a 50-μL amplification reaction, without any pre-amplification processing. The clinical performance of the assay was validated using 88 samples from New York patients suspected of malaria or babesiosis. The overall sensitivity of the assay was 96.6% (95% CI, 87.3% to 99.4%), and the specificity was 100% (95% CI, 85.4% to 100%), compared with gold standard microscopy and a laboratory-developed molecular assay, respectively. The analytical sensitivity was 50 copies of DNA per assay or 200 parasites per microliter of blood, and the assay can detect samples with parasitemia levels <1%. This novel molecular diagnostic assay requires minimal laboratory instrumentation and uses un-processed blood as input; it can be readily performed in the field.

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...

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