Extensively Drug-Resistant Tuberculosis, China

disease in an immunocompromised patient. However, most cases of M. fortuitum pneumonia were reported before the use of molecular technology for species identifi cation. Newer species such as M. mageritense resemble M. fortuitum and would not have been differentiated without this method. Our patient met the criteria for diagnosing nontuberculous mycobacterial lung disease as established by the American Thoracic Society and the Infectious Diseases Society of America (9). Her therapeutic response also supports a cause-and-effect relationship. The identity of an RGM isolate as M. mageritense may be suspected by its unusual antimicrobial drug susceptibility pattern, which showed an intermediate MIC to amikacin and resistance to clarithromycin at 3 days (Table). However, defi nitive identifi cation requires molecular methods. Previous studies have shown that M. mageritense contains an inducible erythromycin methylase gene (erm 40) that confers macrolide resistance (10). The use of molecular studies and greater attention to susceptibility patterns should enable increased recognition of M. mageritense as a human pathogen.