Nontuberculous

Nontuberculous refers to nontuberculous mycobacteria (NTM), a diverse group of mycobacteria other than Mycobacterium tuberculosis complex and Mycobacterium leprae. NTMs are environmental organisms found in soil, water, and biofilms, including household plumbing. Infections result from inhalation or inoculation and occur especially in people with lung disease or weakened immunity. Most NTMs are not spread person to person, though rare clusters can occur in healthcare settings.

NTMs are divided into rapid growers (colonies in about seven days) and slow growers. Common rapid growers include Mycobacterium fortuitum, M. chelonae, and M. abscessus. Slow growers include the Mycobacterium avium complex (M. avium and M. intracellulare), M. kansasii, and M. malmoense.

Clinical disease varies by species and host. Pulmonary disease is most frequent, especially in older adults with chronic lung disease or bronchiectasis, presenting with cough and fatigue. Skin and soft tissue infections occur after trauma or surgery. Immunocompromised patients may develop disseminated or extrapulmonary disease.

Diagnosis relies on repeated isolation from the relevant site, acid-fast staining, culture, and species-level identification by sequencing or line-probe assays, plus imaging. Susceptibility testing informs treatment decisions.

Treatment is species-specific and typically long, often macrolide-based regimens continued for about 12 months after culture conversion. Some organisms, especially M. abscessus, are difficult to treat and may require additional drugs or surgery. There is no vaccine, and prevention focuses on minimizing exposure in vulnerable individuals.