Classification Algorithm for Subspecies Identification within the Mycobacterium abscessus Species, Based on Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry

Mycobacterium abscessus , as a species, has been increasingly implicated in respiratory infections, notably in cystic fibrosis patients. The species comprises 3 subspecies, which can be difficult to identify. Since they differ in antibiotic susceptibility and clinical relevance, developing a routine diagnostic tool discriminatingMycobacterium abscessus at the subspecies level is a real challenge. Forty-threeMycobacterium abscessus species isolates, previously identified by multilocus sequence typing, were analyzed by matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS). A subspecies identification algorithm, based on five discriminating peaks, was drawn up and validated by blind identification of a further 49 strains, 94% of which (n = 46) were correctly identified. TwoM. abscessus subsp.massiliense strains were misidentified asM. abscessus subsp.abscessus , and for 1 other strain identification failed. Inter- and intralaboratory reproducibility tests were conclusive. This study presents, for the first time, a classification algorithm for MALDI-TOF MS identification of the 3M. abscessus subspecies. MALDI-TOF MS proved effective in discriminating within theM. abscessus species and might be easily integrated into the workflow of microbiology labs.