Multi-center evaluation of the VITEK® MS system for mass spectrometric identification of non-Enterobacteriaceae Gram-negative bacilli

Abstract

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.

Evaluation of the Vitek MS Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry System for Identification of Clinically Relevant Filamentous Fungi

“…Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has been utilized in the clinical microbiology laboratory for rapid and accurate identification of bacteria, mycobacteria, and yeasts (2)(3)(4)(5)(6)(7)(8)(9). For filamentous fungi, databases have been limited, and unlike bacteria, filamentous fungi require additional processing steps to disrupt the cell wall, extract proteins, and inactivate the isolate (10).…”

The Ongoing Revolution of MALDI-TOF Mass Spectrometry for Microbiology Reaches Tropical Africa

“…11,[16][17][18][19] Overall, MALDI-TOF MS identification has been found to be highly accurate for clinically relevant bacteria, including Gram-positive, Gram-negative, and fastidious anaerobic bacteria as well as fungi detected in routine microbiology. 11,16,18,20 Herein, we confirm the power of MALDI-TOF MS in identifying bacteria and fungi, with 94.2% identification accuracy at the species level of isolates tested in a laboratory in tropical Africa (2,289 of 2,430 isolates). In the pioneering work performed in 2010 in our laboratory in Marseille, France, 84.1% of 1,660 tested isolates were accurately identified at the species level, and 11.3% of tested isolates were accurately identified at the genus level.…”

“…Other misidentifications rarely observed but also previously reported were within the genera Achromobacter, Burkholderia, and Aeromonas. 16 Most of these misidentifications can be attributed to an incomplete population of databases associated with the instrument. 1,7,18,21,22 For instance, it has recently been reported that improvements to the database enable a more reliable distinction between S. pneumoniae and viridans group streptococci.…”

“…Currently, the estimated wait for one bacterial identification is reported to be from 1 minute and 46 seconds to 2 minutes per sample. 6,16 The use and necessity of this new system were quickly shown by the fact that traditional phenotypic systems were abandoned on the arrival of the MALDI-TOF MS in the laboratory. The rapid and accurate identification of routinely encountered bacterial and fungal species as well as those that are rare and difficult to identify using phenotypic methods provides a promising way to improve the care of patients with infectious diseases in Africa.…”

“…This technique can provide microorganism identification up to 30 hours faster than conventional phenotypic methods; such gains in the speed of identification can have a substantial impact on patient care and management. 6,16,21 MALDI-TOF MS can also be used for the rapid and effective identification of microorganisms from positive blood cultures within 30-45 minutes after a positive signal is provided by a blood culture instrument, and such rapid identification can lead to earlier initiation of treatment with appropriate antimicrobial therapies and increase the chances of obtaining optimal clinical outcomes. 28 The primary obstacle to the use of MALDI-TOF MS in Africa is the cost of the machine.…”