Nontuberculous Mycobacteria (NTM)

Nontuberculous mycobacteria are a group of bacteria that live in soil, swamps, and water sources. 

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Summary
  • Nontuberculous mycobacteria are a group of bacteria that live in soil, swamps, and water sources.
  • Mycobacterium abscessus (M. abscessus) and Mycobacterium avium (M. avium Complex or MAC) are the most common types of NTM found in people with cystic fibrosis.
  • The decision to treat NTM depends on other positive cultures, symptoms that suggest lung disease, such as weight loss, decreased energy, chronic fevers, night sweats, and trends in your lung function.

There are more than 100 types of nontuberculous mycobacteria (NTM), and more are being found every year. NTM are very hardy and can survive many disinfectants and severe environmental conditions. Mycobacterium abscessus (M. abscessus) and Mycobacterium avium (M. avium Complex or MAC) are the most common types of NTM found in people with cystic fibrosis.

The group of bacteria that make up the different types of NTM are “cousins” to the bacteria that cause tuberculosis (TB). These were often called “atypical mycobacteria” in the past. Despite this relationship, NTM are distinct and cause a different lung disease than TB.

NTM and CF

NTM have been found in the sputum of a growing number of people with CF since the 1990s. NTM can cause infections in many organs of the body, but for people with CF, the infection is nearly always in the lungs and can cause NTM lung disease. In 2017 in the US, approximately 13% of people with CF had a positive culture for a NTM species. From 2010 to 2016, 20% of people with CF grew NTM at least once.

NTM can enter the lungs directly through exposure to the environment. Because the organisms live in so many different environments, it is difficult to avoid all possible environmental sources of infection. Consider taking steps to limit breathing in water, soil, or dust. It is unclear if NTM can be passed from one person to another, so consider taking precautions to minimize the risk of cross-infection. 

In North America, nearly 75% of NTM are MAC and 25% are M. abscesses. In general, MAC is seen in older people who have more mild disease and M. abscessus is associated with more advanced disease and a more rapid decline in lung function. 

Diagnosing NTM Lung Disease

NTM lung disease can be challenging to diagnose. NTM is diagnosed by analyzing special cultures of your sputum for the presence of NTM. NTM infections can be detected only if these special cultures are ordered by your doctor. Clinical guidelines recommend yearly screening for NTM.

Sputum samples can be taken from what you cough up, from sputum-induction (with saline), or from bronchoscopy (when a fiber-optic tube is passed into your lungs to get samples). To help make sure the test is accurate, the sample must be taken from the lungs and not from a throat swab.

An important thing to remember is that even if NTM is found in your sputum culture, it does not mean that you have NTM lung disease. Typically, after a positive culture for NTM, your doctor will confirm it with one or more additional cultures. If cultures for NTM are repeatedly positive, your doctor may get a high-resolution chest computed tomography (CT) scan to look for clues of NTM disease and find out its extent.  Unfortunately, even with a CT scan, it can be difficult to distinguish NTM lung disease from the normal findings seen in CF lung disease in people who do not have NTM lung disease.

Even if NTM is found in your sputum culture, it does not mean that you have NTM lung disease.

NTM can take up to eight weeks to grow, so you may have to wait some time until you receive your results. This slow growth makes NTM much harder to diagnose and treat.

Treating NTM Lung Disease

Like typical CF infections from Pseudomonas aeruginosa and Staphylococcus aureus, NTM can chronically infect (“colonize”) the airways. Most people with a single positive NTM culture will not require treatment. The decision to treat NTM depends on other positive cultures, symptoms that suggest lung disease, such as weight loss, decreased energy, chronic fevers, night sweats, and trends in your lung function.

Because infections with typical CF bacteria can have similar features and are so common, your CF care team may treat these bacteria aggressively to see if your symptoms and lung function improve. If they do not, it may suggest NTM lung disease. Although NTM is naturally resistant to many antibiotics, treatments are available and research is underway to find more.

Once you and your CF care team decide that you should be treated for NTM lung disease, you will likely be started on at least three antibiotics at the same time. You may need to take these antibiotics for 12 months or longer. Because you would be taking so many medications for such a long period of time, it is important to review any possible interactions with your other medications with all your medical providers and pharmacist.

The goal is to decrease the amount of infection in your lungs. By doing this, your care team will try to improve your symptoms and decrease the amount of damage to your lungs. It may also mean your sputum will no longer grow NTM, although this does not happen in all individuals.

Treatment is typically divided into two phases: an intensive first phase followed by a continuation phase. During the first phase, you will usually take oral antibiotics, as well as an intravenous (IV) antibiotic. During the continuation phase, you may take one or more oral antibiotics, and possibly an inhaled antibiotic. 

The exact combination of antibiotics that your doctor prescribes will depend on the type of NTM that is in your lungs. Tests will determine which antibiotics are the best at treating your particular infection. More tests are done to watch for side effects or allergies that you might develop during months of treatment.  

You will be asked to provide blood samples routinely to monitor levels of the drugs in your body. You may also need to have your hearing and vision tested regularly. This is to check for signs of toxicity caused by some antibiotics. 

Your doctor may frequently change your medications during NTM treatments if you experience side effects or allergies that begin to interfere with your quality of life or are potentially harmful. More information about medications used to treat NTM lung disease and their side effects can be found at ntminfo.org.

In addition to the NTM medications, it is very important to continue your standard CF medications and airway clearance. Often, people with CF and NTM need to do more airway clearance than usual.

Research on NTM

Since 2010, the Foundation has carefully tracked NTM in its Patient Registry at the species level and is working with researchers to identify risk factors that make people with CF more likely to get NTM. Learn more about research on NTM. Talk to your care team about new research and possibilities of participating in clinical trials related to NTM and CF.

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