What Are Nontuberculous Mycobacteria?

In This Article

Tuberculosis (TB) is one of the most common infectious diseases in human history. The lung infection is caused by a type of bacteria called mycobacteria. There are over 100 species of mycobacteria and while the one that causes TB might be the most well-known, it’s not the only one that can make humans sick.

Several species of mycobacteria called nontuberculous mycobacteria (NTM) are common in the environment. Humans come into contact with them regularly and usually do not get sick. However, some people who have certain health conditions, weak immune systems, or other risk factors can become ill if they are exposed to NTM.

Here’s an overview of the different species of nontuberculous mycobacteria (NTM) that have been found in humans, the type of illness each type can cause, why some people get sick and others do not if they come into contact with the bacteria, as well as how an NTM infection is diagnosed and treated.

Types of Nontuberculous Mycobacteria

Scientists have identified more than 180 species of nontuberculous mycobacteria (NTM), many of which are found in humans. The bacteria are common in the environment, especially water and soil, and often find their way onto (or into) our bodies. Most people do not get sick of they are exposed to most species of NTM.

When humans and bacteria are together in the same environment and are not affected by one another, it’s called a commensal relationship.   

Mycobacteria have been found all over the world. Certain types tend to be found in certain environments, however. For example, in the United States, M. abscessus is most commonly found in the southern states.

The mycobacteria that cause tuberculosis is the most well-known of this group, so the other types of mycobacteria that do not cause TB are grouped together and called nontuberculous mycobacteria. They are also sometimes called “atypical mycobacteria,” “mycobacteria other than tuberculosis (MOTT),” or “environmental mycobacteria.”

Rapid vs. Slow-Growing

Within the big group, scientists who study bacteria (microbiologists) divide the species of NTM further according to how fast they can grow them in a lab. Each species is either rapid-growing or slow-growing.

Rapid-growing NTM (seven to 10 days):

  • M. abscessus complex
  • M. chelonae
  • M. fortuitum
  • M. mucogenicum

Slow-growing NTM (14 days or more):

  • M. avium and M. intracellulare (often called M.avium complex)
  • M. chimaera
  • M. kansasii

How It Spreads

Mycobacteria are a normal part of our environment and we encounter them regularly as we go about our daily lives. Most of the time, we just live with these bacteria but they don’t make us sick. However, they are opportunistic pathogens—which means they are looking for a host to live in. Sometimes, a human ends up being a good host.

Humans come into contact with mycobacteria when they are outside, such as through water or soil. When particles of water, dirt, or dust that contain mycobacteria get into the air (aerosolization), people can breathe them in.

People can also be exposed to mycobacteria inside buildings, such as their house or apartment, or in their community, such as in a hospital or school. People with certain jobs are more likely to be exposed to mycobacteria in the workplace. For example, a person who works at a salon, spa, or tattoo parlor.

When someone is exposed to mycobacteria inside a building, it’s often because the bacteria has made its way into a local water supply (plumbing, including bathroom showers) or air circulation systems (such as air conditioning units).

Mycobacteria like to live in moist environments (where water and warm air come together), such as a spa.

Nontuberculous Bacteria Symptoms

Both rapid- and slow-growing NTM can make humans sick. While a lot of infections occur in the lungs, mycobacteria can also infect other parts of the body. The symptoms of NTM infection can be general, vague, and nonspecific, but can also be related to where in the body the bacteria is.

The symptoms related to NTM infection are usually grouped by the system of the body that is infected. The most common is the respiratory system, but NTM also commonly affects the skin (such as in surgical wounds).

When a person is already sick from another illness and has a weak immune system, NTM can become widespread throughout the body. This is referred to as a disseminated infection (or disseminated disease).

People with HIV/AIDS, cancer, or chronic diseases of the lungs (such as cystic fibrosis) are most at risk for developing disseminated NTM infection.

If a person is infected by NTM and feels sick, they may have general signs and symptoms. For example, they might have a fever and a cough, which are common to many illnesses and not specific to NTM infections.

Extrapulmonary Infections

When NTM infects an area outside of the lungs, it’s called an extrapulmonary infection. These infections are less common and usually found in an implanted medical device (like a pacemaker) or a surgical wound.

However, it’s usually not clear just by looking at the site of the infection (which could be red and swollen) that NTM is the cause. Samples are taken from the soft tissue and tested for NTM. 

For the most part, symptoms that are caused by an NTM infection depend on the part of the body that is affected. The severity also depends on a person’s overall state of health. Rashes, shortness of breath, weakness, and weight loss have been reported, and are usually worse in people who are sick with another illness, such as HIV.

Some symptoms of NTM infections are more common in children, such as swollen lymph nodes.

Causes

NTM usually does not make people sick, even if they come into contact with it directly. In fact, if tested, most people will have NTM on or in their bodies but are not ill from it.

Usually (but not always), an illness caused by NTM happens because someone was already in an ill state of health. People with certain medical conditions, especially those that affect the lungs, are more susceptible to infection with NTM and tend to have a harder time getting better.   

If a person does not have a strong immune system not only does it make them more likely to get an infection, it also makes it harder for their body to heal. If NTM is present in their environment (for example, in the air or water), they are vulnerable to becoming infected.

Carriers and Contagiousness

A healthy person can have NTM in their body and not get sick. In fact, even if a test showed the bacteria on a person’s body, it does not mean they are infected. The person can be carrying the bacteria without being infected. Being a carrier does not mean they will spread the bacteria to someone else and make them sick.

Unlike TB, NTM is not considered to be contagious. NTM is not like the bacteria that causes TB, which can be spread between people. Person-to-person transmission has not been seen with NTM. It’s also not clear if people can get NTM from an animal. However, animals and people in living the same area might all become infected by NTM if they use the same source for drinking water (such as on a farm).

Most NTM infections occur because someone comes into contact with the bacteria in their environment—usually, because it is in the water or air.

Who Gets Sick?

Researchers aren’t sure exactly how many NTM infections (both those that cause symptoms and those that are asymptomatic) happen in a given year. Unlike TB, states are not required to report NTM infections to the public health department.

That said, if people in the same community or geographic area have the same symptoms and are all found to have NTM when tested, health professionals will usually try to find a common source of exposure (such as a river near a town’s water supply).

People who are at high risk might be advised to avoid water sources that could contain NTM. For example, they might be told to use well water, if possible, to reduce the chance of being exposed to NTM as well as other bacteria that could make them sick.

Research and data from scientists who study diseases at the population level (epidemiologists) indicate that NTM infections appear to be more common in women than men and older people are more likely to have an infection than younger people (though it can occur in children).

While it’s uncommon, it is possible for a person to have multiple infections caused by more than one type of NTM at the same time. These “co-infections” are harder to treat and are more likely to come back (recur).

One example of NTM co-infection is M.avium complex, which is caused by mycobacterium avium and mycobacterium intracellular. The infection usually occurs in people who have a disease that makes their lungs especially vulnerable, such as cystic fibrosis, and a weak immune system. 

Elderly women who are very frail and thin, have a condition affecting their heart called mitral valve prolapse, and/or skeletal conditions like scoliosis or pectus excavatum may also be more likely to have a severe illness from NTM (especially when it is in the lungs).

While the research is still new, some studies have suggested that there might be genetic factors that make a person more likely to get sick from NTM. Certain genetic disorders of the immune system have also been identified as increasing a person’s risk for severe (disseminated) NTM disease.

Diagnosis

When someone goes to the doctor with symptoms like a fever, cough, or rash, there could be many possible causes for their illness. Some of them are more serious than others, but it’s likely that their symptoms are being caused by an infection or illness that is more common than NTM.

NTM infections that make someone seriously ill are uncommon. They are more likely to happen in people who are already ill from a chronic health condition like HIV, or those having treatments that make their immune system weak.

If an otherwise healthy person has symptoms, a doctor will likely test them for more common causes before considering NTM. However, if someone who is more susceptible to infection has symptoms (especially when they are not explained by other types of infections) a doctor is more likely to consider testing for NTM sooner.

In general, NTM infections are not common. Doctors do not routinely test for these infections and have to strongly suspect it as a cause before they order tests to check for it.

Tests

The tests used to look for NTM are not available at every lab. While most hospitals and clinics can test for more common bacterial infections, NTM is not typically included. A doctor might have to send a patient’s specimen (usually sputum or blood) to a special lab to be tested for NTM.

The lab will perform a type of test called a culture. They take the sample of fluid from a patient’s body and let it grow under specific conditions in the lab. They check the culture to see what type of bacteria is growing, how much is growing, and how long it is taking to grow.

NTM usually takes several weeks to be cultured and grown in a lab. If a doctor thinks a patient might have NTM, it can take a long time to get the results. In the meantime, a doctor might do other tests—like a chest X-ray—to see if there are other infections or injuries.

Genetic tests can also be used to help identify NTM. One is called a nucleic acid amplification test. It can help labs tell which type of NTM they are seeing in a patient’s culture.

To confirm the diagnosis, a patient must have symptoms that are common in people with NTM and a positive lab test that shows a type (or more than one type) of NTM in their body.

Healthcare professionals that encounter NTM infections should report them to the local health department—especially if they think more than one person might be (or get) sick.

While it can be difficult to get, a timely and accurate diagnosis is important. Before a person can get treatment for NTM, a doctor needs to know which type of NTM is in their body.

Treatment

If someone is diagnosed with an infection caused by NTM, they might need to see a specialist. Infectious disease doctors are trained to handle illnesses that are caused by bacteria, viruses, and other pathogens. A pulmonologist can help someone with a serious lung infection that is caused by NMT.

Medication

The treatment for NTM will depend on where the infection is. In most cases, people with NTM anywhere in their body need to take antibiotic medications—usually for a long time. They might need to take more than one type of medication. Some will need to have the medication in an IV, usually at a hospital or infusion center. Other people will only need to take the medication as a pill.

A person being treated for NTM may need to take one or more of the following classes of antibiotics:

  • Aminoglycosides
  • Ethambutol
  • Fluoroquinolones
  • Imipenem
  • Linezolid
  • Macrolides
  • Rifamycins

The treatment for serious NTM disease can last a year or more. During this time a person might feel better and may even have tests that show NTM is no longer in their body. However, they still need to finish the entire course of treatment to help prevent the infection from coming back.

Supportive Care

While someone is taking antibiotics, their doctor might give them other treatments that are specific to where the infection is located. These supportive treatments are to help the person feel better and prevent further infection.

For example, a person who has NTM in a wound would need to have routine wound care and someone with NTM in their lungs might need to have treatments to help clear mucus and help them breathe.

After a person completes treatment, they will usually need to be tested for NTM several more times (in some cases, for several years after the infection) to ensure that it has not come back.

Prognosis

People with infections caused by NTM can recover as long as they receive treatment. Since the infections are not common, it can sometimes be difficult for a doctor to make a quick diagnosis and start treatment. Sometimes, people have NTM infections for a long time (chronic) before a diagnosis is made and treatment is started.

The treatment for NTM infections is long and can be difficult, but when patients stick with it and get the appropriate supportive medical care, they can recover. If they are at risk of getting the infection again, there are steps that they can take to reduce their risk.

Antibiotic Side Effects

When someone has to take antibiotic medications for a long time, they might have side effects that are hard to deal with on a day-to-day basis. Usually, their doctor can help them cope with these symptoms (such as gastrointestinal upset) but people might also want to look for other, complementary, strategies to help them get through their treatment. 

Long-term Health Problems

Some people who get NTM infections develop long-term health problems. This can happen if the infection goes undiagnosed and untreated for a prolonged period.

For example, a person might have severe (if not permanent) damage to their lungs or may develop a wound infection that is bad enough that a limb needs to be amputated.

People who are infected with more than one NTM type at the same time (such as people with HIV who develop MAC) are more likely to have a poor prognosis.

Infection Prevention

In some cases, a person might be advised to make some changes to their lifestyle. If a person is at risk for another infection caused by NTM and a doctor suspects they contracted it from the local water supply, they might suggest that the person only drink well water or use bottled water.

If they think the person picked up the bacteria in soil, they might recommend that they stop working in the garden or take special precautions to protect themselves from inhaling any particles.

Coping

There are online resources and support groups for people with NTM infections. Organizations like the American Thoracic Society, the American Lung Association, the National Center for Advancing Translational Sciences, the National Institutes of Health, and the Centers for Disease Control and Prevention also offer reliable information for patients and their families.

A Word From Verywell

It can be hard to diagnose NTM infections because they are not common and some of the tests are not available at every hospital. However, an accurate and timely diagnosis is important. The sooner a person knows they have an infection caused by NTM, the sooner they can be treated.

The treatment for NTM depends on where the infection is, but usually involves a long course of multiple antibiotics). If people adhere to the treatment (which can be up to a year and involve more than one medication) they can recover. Researchers are still learning about NTM and working to develop more effective ways to diagnose and treat the infections it can cause.

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Article Sources
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  4. Centers for Disease Control and Prevention. Nontuberculous mycobacteria (NTM). Patients. Updated August 2019.

  5. National Center for Advancing Translational Sciences, Genetic and Rare Diseases Information Center (GARD). Mycobacterium Avium Complex infections. Updated November 2018.

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