Evaluation of the Vitek MS v3.0 Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry System for Identification of Mycobacterium and Nocardia Species

Abstract

This multicenter study was designed to assess the accuracy and reproducibility of the Vitek MS v3.0 matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry system for identification of and species compared to DNA sequencing. A total of 963 clinical isolates representing 51 taxa were evaluated. In all, 663 isolates were correctly identified to the species level (69%), with another 231 (24%) correctly identified to the complex or group level. Fifty-five isolates (6%) could not be identified despite repeat testing. All of the tuberculous mycobacteria (45/45; 100%) and most of the nontuberculous mycobacteria (569/606; 94%) were correctly identified at least to the group or complex level. However, not all species or subspecies within the ,, and complexes and within the and groups could be differentiated. Among the 312 isolates tested, 236 (76%) were correctly identified to the species level, with an additional 44 (14%) correctly identified to the complex level. Species within the and complexes could not always be differentiated. Eleven percent of the isolates (103/963) underwent repeat testing in order to get a final result. Identification of a representative set of and species was highly reproducible, with 297 of 300 (99%) replicates correctly identified using multiple kit lots, instruments, analysts, and sites. These findings demonstrate that the system is robust and has utility for the routine identification of mycobacteria and in clinical practice.

Antimycobacterial Susceptibility Testing of Nontuberculous Mycobacteria

“…abscessus are known to have a nonfunctional erm(41) gene, and these isolates will remain macrolide susceptible even after 14 days of incubation (20). Although the matrix-assisted laser desorption ionizationtime of flight (MALDI-TOF) method is gaining popularity in clinical laboratories, it cannot identify the M. abscessus complex to the subspecies level, which is critically important for selection of treatment (24,25).…”

Fatal pulmonary infection by trimethoprim-sulfamethoxazole resistant Nocardia otitidiscaviarum: report of two cases and review

“…Identification of Nocardia spp. using MALDI-TOF was also found to be highly reproducible with 99% of replicates correctly identified using multiple kit lots, instruments, analysts, and sites [43].…”

First case of fatal bacteremia due to Nocardia neocaledoniensis

“…Its performance was evaluated by Body et al on a panel of 312 isolates representing 21 different Nocardia species. Of the 312 isolates, 3 % were incorrectly classified by this method, including 3 strains of N. asteroides which were misidentified as N. neocaledoniensis [ 9 ]. Concerning Nocardia bacteremia, the last study of Williams et al reported more than 100 cases of invasive infections [ 10 ].…”