Matrix-assisted laser desorption ionization-time of flight mass spectrometry can accurately differentiate between Mycobacterium masilliense (M. abscessus subspecies bolletti) and M. abscessus (sensu stricto)

Abstract

Among 36 Mycobacterium masilliense and 22 M. abscessus isolates identified by erm(41) PCR and sequencing analysis of rpoB and 23S rRNA genes, the rate of accurate differentiation between these two subspecies was 100% by cluster analysis of spectra generated by Bruker Biotyper matrix-assisted laser desorption ionization-time of flight mass spectrometry.

Fig 1

(A) Two clusters of M. abscessus complex spectra, i.e., cluster 1 (M. massiliense) and cluster 2 (M. abscessus [sensu stricto]), analyzed by clustering analysis of MALDI-TOF MS results. (B) The six peaks used to define cluster 1 (M. massiliense) and cluster 2 (M. abscessus [sensu stricto]), which were generated by ClinProTools with the genetic algorithm, are 4,386.24 m/z, 7,639.70 m/z, 7,669.20 m/z, 8,771.73 m/z, 8,783.84 m/z, and 9,477.48 m/z. The signals of 4,386.24 m/z, 7,669.2 m/z, and 8,771.73 m/z were observed in cluster 1 spectra but not in cluster 2 spectra, and those of 7,639.7 m/z, 8,783.84 m/z, and 9,477.48 m/z (class 2) were observed in cluster 2 spectra but not in cluster 1 spectra. The absolute intensities of the ions are shown on the y axis, and the masses (m/z) of the ions are shown on the x axis. The m/z values represent the mass-to-charge ratio.

Fig 2

Distribution of MICs of clarithromycin against M. massiliense (n = 36) and M. abscessus (sensu stricto) (n = 22) determined by the Sensititre RAPMYCOI panel test (TREK Diagnostic Systems). Results were read on the 5th day of incubation and on day 14 (extended incubation).