Long-term relapses after 12-month treatment for Mycobacterium kansasii lung disease.

Long-lasting therapy for Mycobacterium kansasii lung disease with rifampin-containing multidrug regimens is needed to avoid relapses. The aim of the present study is to evaluate a short multidrug treatment regimen for M. kansasii lung disease. A retrospective observational study of 75 patients with M. kansasii lung disease was conducted in a teaching hospital from January 1990 to December 2005. In total, 75 (67.6%) out of 111 patients diagnosed with M. kansasii lung disease completed a 12-month multidrug treatment regimen, including rifampin, isoniazid and ethambutol, supplemented with streptomycin during the first 2-3 months. After a 41.5-month median follow-up, five (6.6%) patients relapsed. The relapse rate was 2.19 (95% confidence interval 0.71-5.12) per 100 person.yrs. Treatment compliance was considered to be appropriate in all five patients and no drug resistance developed in any case. In conclusion, a 12-month fixed-course treatment is effective in most cases of Mycobacterium kansasii lung disease, but may not be long enough for all patients.