[A possible case of pulmonary infection due to Mycobacterium heckenshornense].

A 68-year-old man with emphysema was admitted with cough and bloody sputum. Chest radiography revealed infiltrative shadows in the right upper lung. Microbiologically, an acid-fast bacillus was detected in the culture of sputum (Gaffky (+)), but both tuberculosis bacillus (TB) and Mycobacterium avium complex (MAC) were negative by the PCR method. Combination chemotherapy, which included isoniazid, rifampicin, ethambutol and pyradinamide, was initiated under a tentative diagnosis of TB. His clinical symptoms and radiographic findings improved. After 4 months, the strain of acid-fast bacilli was identified as Mycobacterium xenopi by DNA-DNA hybridization (DDH) method. However, analysis of base sequences from sputum samples using 16S rDNA confirmed the identity of all tested isolates as Mycobacterium heckeshornense. M. heckeshornense could not be identified by the DDH method in Japan. When M. xenopi is detected, it is essential to perform both sequencing of 16S rDNA and a biochemical method for the purpose of distinguishing M. heckeshornense from M. xenopi.