Treatment of pulmonary disease caused by Mycobacterium kansasii.

As a cause of lung disease (LD), Mycobacterium kansasii is regarded as a highly virulent species among nontuberculous mycobacteria (NTM). Both the frequency of M. kansasii isolates and global prevalence of M. kansasii-LD have increased gradually over recent decades. Treatment of M. kansasii-LD is recommended because of the disease's poor prognosis and fatal outcome. The decision on the optimal time point for treatment initiation should be based on both the benefits and risks posed by multiple antimicrobial agents. For treatment-naïve patients with M. kansasii-LD, rifampin-containing multiple antimicrobial regimens for ≥12 months after culture negative conversion are effective. However, some challenges remain, such as determining the precise length of treatment duration as well as addressing intolerable adverse effects, the uncertain effectiveness of isoniazid and ethambutol in treatment, the uncertain correlation between in vitro drug susceptibility testing and clinical outcomes, and the increasing prevalence of clarithromycin-resistant M. kansasii isolates. Short-course and effective therapies must be developed. New candidate drugs, such as tedizoid and clofazimine, exhibit excellent antimycobacterial activity against M. kansasii in vitro, but in vivo studies of their clinical applications are lacking. This paper reviews the treatment, outcomes and future directions in patients with M. kansasii-LD.