Abstract
Using the MALDI Biotyper (Bruker), we verified the strains identified as Mycobacterium intracellulare by the COBAS TaqMan MAI. We compared the critical threshold (CT) value to evaluate the misidentification by COBAS TaqMan MAI. Furthermore, we reviewed the medical records of patients to analyze the characteristics of the discrepant strains. The discrepant strains identified by the MALDI Biotyper were M. lentiflavum (4/70), M. colombiense (2/70), M. marseillense (1/70), and M. arosiense (1/70). There was a significant difference in the CT value between M. lentiflavum and the other species. As for the virulence, combined treatment with antibiotics was not administered to the patients in whom the strains of M. lentiflavum (2/3) were isolated from sputa. We consider that the virulence of M. lentiflavum is different from that of M. intracellulare commonly causing pulmonary disease; therefore, accurate identification is important. On the other hand, the strains of M. colombiense (2/2) were isolated from skin lesions. Because infection with M. colombiense is very rare, the accumulation of cases is expected. In conclusion, the identification accuracy of the MALDI Biotyper is comparable to that of the molecular diagnostic method, and the MALDI Biotyper is useful for routine diagnostic tests. Moreover, it is considered that the misidentification of M. lentiflavum can be detected by confirming the CT value when COBAS TaqMan MAI identifies M. intracellulare.
