Clinical and radiological features of Mycobacterium kansasii and other NTM infections

Mycobacterium kansasii infection is one of the most common causes of nontuberculous mycobacterial lung disease in the world. However, it is not possible to differentiate completely between M. kansasii and other nontuberculous mycobacteria (NTM) because of a lack of direct comparative studies. This retrospective study sought to identify their clinical and radiological features systematically.

The sample included 98 consecutive patients with a culture-positive diagnosis of NTM infection, derived from the databases of the Laboratory of Microbiology of a tertiary medical center and two outpatient tuberculosis centers. Sixty-four patients had M. kansasii infection. All patients fulfilled disease criteria for treatment. Data on patient background and clinical features were collected, and chest radiographs were evaluated.

In the M. kansasii group, n = 27 (42%) were native-born Israelis compared to 9.4% (n = 3) of all other NTM groups (p = 0.0001). Similar rates of co-morbid diseases, including diabetes mellitus, heart disease, lung diseases, and malignancy were noted in both groups. Old TB was less common in the M. kansasii group compared to the other NTM (3.1% vs. 23.5%, p = 0.003). Clinical symptoms were significantly more common in patients with M. kansasii infection. On radiological study, M. kansasii infection was associated with more cavitations and unilaterality. Patients with M. kansasii infection had a higher likelihood of right upper lobe disease (p = 0.001). Pleural effusions and lymphadenopathy were found only in a few patients in each group.

Major differences in the epidemiologic and clinical features of M. kansasii infection and other NTM have important diagnostic and clinical implications.