Nontuberculous Mycobacteria Week

General Information

Nontuberculous Mycobacteria Week

Nontuberculous mycobacteria (NTM), of which more than 150 species have been identified, are ubiquitous in the environment. The most common organisms causing human disease include Mycobacterium avium complex (MAC), M.abscessus, and M. kansasii, among others. They can cause pulmonary, skin, soft tissue, and rarely, disseminated infection. Unlike tuberculosis, there has been no convincing evidence of human to human transmission of the pathogens.

The overall prevalence of NTM pulmonary infection in United States is not well established, but recent studies have reported an increased incidence and prevalence over the past two decades. NTM infection also appears to be more common than tuberculosis. MAC is the most common causative pathogen. There is geographic variability in the US; Hawaii has the highest prevalence, while other areas such as Southeastern Pennsylvania, also have large numbers of cases. Women are generally more likely to have infection than men. The specific factors that confer susceptibility to the disease remain unclear, but anatomic factors such as pre-existing bronchiectasis, underlying lung disease such as COPD or prior cavitary lung disease, immunosuppression and environmental factors have all been postulated to be contributing factors.

NTM infection may be associated with significant respiratory and systemic symptoms such as cough, sputum production, fever, fatigue and weight loss, and negative impact on overall quality of life. The diagnosis of pulmonary NTM infection requires the presence of pulmonary symptoms, characteristic abnormal findings on chest imaging, exclusion of other diagnoses, and ultimately, microbiological confirmation.

Significant controversy exists regarding the indications for and duration of therapy as well as the optimal drug regimen. Current thinking is that establishing a diagnosis of pulmonary NTM infection does not necessarily require treatment in all patients. The ultimate decision is based on careful consideration of the benefits of therapy weighed against the potential risks of the medications for individual patients. In general, NTM infections require treatment with multiple agents, the specifics of which are guided by the specific pathogen and drug susceptibility testing. For MAC, a typical initial regimen includes a macrolide, ethambutol and rifampin. Prolonged therapy for as many as 18 months is typically required. Careful monitoring during treatment is important. Surgical resection may have a role in the treatment of some NTM infections in the lung.

The natural history and prognosis of pulmonary NTM infection are variable, and additional study is required to more precisely establish them. Factors that have been reported to negatively impact prognosis include older age, low BMI, anemia and cavitary disease by chest CT scan.

Infection with NTM poses a formidable clinical challenge. Ultimately, more basic and clinical research is necessary to address this challenge, help guide clinicians and patients, and establish more evidence-based treatment regimens.

Four Facts About NTM

  1. Mycobacteria are naturally occurring environmental organisms found widely in both water and soil and can cause significant respiratory damage.

  2. People with underlying lung disorders such as COPD, Alpha-1 Antitrypsin ‎Deficiency, Cystic Fibrosis, Bronchiectasis and others, are at greater risk for NTM infection

  3. NTM can be difficult to diagnose and is often mistaken for tuberculosis. Delay in treatment can result in additional damage to the respiratory system.

  4. The exact number of pulmonary NTM patients in the United States is not known. Past studies estimated the number between 50-90 thousand people at any given time, however new data shows diagnosis is increasing at about 8% per year.