Four cases of Mycobacterium xenopi pulmonary disease

: Mycobacterium xenopi is very rare pathogen in Japan. We reported herein four cases of M. xenopi pulmonary disease. These patients were all male and their ages ranged from 53 to 72. They all had past history of pulmonary tuberculosis, including two cases who had been also treated for Mycobacterium kansasii pulmonary disease later. The bacilli could be cultured in Mycobacteria Growth Indicator Tube (MGIT) system from 10 sputum samples, but they could not be cultured on Ogawa egg media except for two samples. All four cases fulfilled the criteria for the diagnosis of nontuberculous mycobacteria pulmonary disease proposed by the Japanese Society for Tuberculosis. Combination chemotherapy including isoniazid, rifampicin, and ethambutol was started in all four cases when mycobacteria were detected under tentative diagnosis of the relapse of tuberculosis or Mycobacterium kansasii disease. Sputum converted to culture negative by the chemotherapy in two cases. In one case, the chemotherapeutic regimen was changed to rifampicin, ethambutol, and clarithromycin after the bacteriological identification of M. xenopi, and the new regimen was found to be effective. In the final case, both of the regimens were finally ineffective.