MALDI-TOF Mass Spectrometry
By setting a LSV cut-off at ≥ 2.0, MALDI-TOF MS was able to correctly
identify 80 isolates out of 111 (72.1%) appertaining to 19 species
using sequence analysis (16s rRNA gene, rpoB and hsp65 ).
By lowering the cut-off for species identification at ≥ 1.8 as
previously proposed for mycobacterial species
(Alcaide et al., 2018,
Pranada, 2015), 100 isolates (90.1%)
from the same 19 species were correctly assigned (Table 1). Two
isolates, one M. vulneris misidentified as M. colombiense(LSV 2.08) and a second one, presumably representing a new species and
misidentified as M. arupense (LSV 1.81) led to discrepant results
(Supplementary material S2-S4). The remaining 9 isolates, classified as
“no identification possible” by MALDI-TOF MS, were identified by
sequence analysis as M. colombiense (3/3 isolates) M.
scrofulaceum (2/2 isolates), M. monacense and M. terraecomplex (one isolate each), and two additional undescribedMycobacterium spp..