Mycobacterium heckeshornense lung infection diagnosed by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS)

Abstract Identification of microorganisms by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has been widely accepted. However, the significance of MALDI-TOF MS for identifying mycobacteria, particularly rare nontuberculous mycobacteria, has not been established. M. heckeshornense is one such bacteria, and distinguishing it from M. xenopi is difficult. The patient was a 40-year-old man with Behҫet's disease who had started treatment with prednisolone and azathioprine. A lung nodule in the right lower lobe was pointed out, and it increased in size 6 months later. Bronchoscopy was performed, and was culture positive for mycobacteria. It was identified as M. heckeshornense by MALDI-TOF MS with a score value of 1.928. Analysis of the 16S rRNA, rpoB , and hsp65 genes confirmed the result of MALDI-TOF MS. MALDI-TOF MS seems reliable for the diagnosis of M. heckeshornense infection.