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Nontuberculous mycobacteria (NTM) are known as atypical mycobacteria. That means they’re related to tuberculosis, but they don’t cause the same disease. In fact, NTM are generally harmless. That’s a good thing. Almost everyone has these microbes in their body.

But infections caused by NTM are on the rise. Groups seeing a bump in cases include middle-aged women, people older than 65, and people using biologics and other immune-suppressing drugs.

But not all NTM infections are caused by the same type of bacteria.  

What Are the Different Types of Nontuberculous Mycobacteria (NTM)?

Scientists have discovered at least 200 NTM species. Here’s a breakdown of some you should know about:

Mycobacterium avium complex (MAC). This includes two related species: mycobacterium avium and mycobacterium intracellulare. MAC is by far the most common type of NTM in the U.S. These slow-growing bacteria typically target the lungs but can affect your whole body.

Mycobacterium kansasii. In the U.S., this is the second most common cause of NTM infection. Like MAC, it usually causes lung disease. But antibiotics can typically get rid of it.

Mycobacterium abscessus complex (MABC). This is a fast-growing group of NTM that mostly causes lung disease. MABC shows up a lot in people with cystic fibrosis, who may be able to pass it to each other. These bacteria are resistant to most kinds of antibiotics.

Mycobacterium ulcerans.Worldwide, this is the third most common mycobacterial infection. It causes a skin infection known as Buruli ulcer. It mostly affects people who live in hot and humid countries.

Mycobacterium marinum. This NTM tends to hang around marine life. But it can sometimes cause a skin infection in healthy humans. You might get these germs on you if you clean a fish tank, pick up seashells, or swim in a pool without chlorine.

How Do Nontuberculous Mycobacteria Get Inside Your Body?

Unlike tuberculosis, NTM infections usually aren’t spread from person to person. But you can easily breathe in or swallow these tiny germs when you’re out in the world.

Where might you come across these microbes in daily life? Lots of places. That’s why they’re known as environmental bacteria.

Common sources of NTM include the following:

  • Dust
  • Water you drink or shower in
  • Lakes, streams, or rivers
  • Steamy places like hot tubs or saunas
  • Dirt, including potting soil

Scientists have also found these germs in:

  • Sewers
  • Tame and wild animals
  • Milk and food products

Some people may be exposed to NTM through medical devices during surgery or other treatments.

NTM can also stick together to form really tough biofilms. These slimy substances cling to wet surfaces like your showerhead or plumbing. Biofilms help bacteria survive by shielding germs from things like antibiotics and disinfectants.

Where Can Nontuberculous Mycobacteria Cause Infection in the Body?

Keep in mind that NTM isn’t a health threat to most people. But these germs can make you sick if your lungs are damaged or your immune system can’t clear bacteria very fast. Your genes and environment also play a role in your immune response.

With that said, NTM can set up shop anywhere in your body. Some spots are affected more often than others. The types seen most often include:

Pulmonary. This is when your lungs and airways are involved. It’s the No. 1 type of NTM infection. It can happen to anyone, but your odds are higher if you:

  • Are older than 65
  • Are a postmenopausal woman
  • Have another lung disease

Disseminated. Sometimes NTM can get in your blood and cause a widespread infection. You’re more likely to get this kind of disease when your immune system isn’t very strong or doesn’t work the right way. This can happen if you have:

  • Advanced HIV/AIDS
  • Blood cancer
  • Organ transplant
  • A condition treated with immune-suppressing drugs
  • Autoimmune conditions like rheumatoid arthritis
  • Genetic immunodeficiency disorders

Lymph node. Also known as lymphadenitis, this is the most common kind of NTM infection among young kids with a normal immune system. It typically causes swollen lymph nodes in the neck that can be treated with surgery.

Skin or soft tissue. Less often, some kinds of NTM can cause sores or swelling in different parts of your body.

When Do You Treat a Nontuberculous Mycobacteria Infection?

That’s a good question. The answer depends on a few things.

Your doctor will consider the location of your infection, how serious your symptoms are, and your overall health. They’ll also pinpoint the type of NTM that’s making you sick. That matters because specific antibiotics are used to target different kinds of bacteria.

Another key question: do you have a fast or slow-growing infection?

You may not need treatment right away if you have a slow-growing form of NTM. That’s bacteria that take a week or two to grow in a lab dish. In real life, these germs can linger in your body for years without causing a lot of damage or making you feel worse.

Most NTM that cause lung disease grow slowly. Ones your doctor might look for include:

  • MAC
  • Mycobacterium chimaera
  • Mycobacterium kansasii
  • Mycobacterium marinum
  • Mycobacterium ulcerans

Fast-growing NTM grow within 7 to 10 days. Some examples include:

  • Mycobacterium abscessus complex
  • Mycobacterium chelonae
  • Mycobacterium fortuitum
  • Mycobacterium mucogenicum

Even slow-growing NTM infections can be serious and tough to get rid of. No matter what’s making you sick, you may need to take two or more antibiotics for a year or two. In some cases, you may need surgery.

Ask your doctor to go over the pros and cons of treatment for NTM infections. They’ll help you decide what’s best for your health and lifestyle.

If you have HIV, talk to your doctor about antiretroviral therapy (ART). Effective ART is your best protection against future infections.

Show Sources

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Pathogens: “Non-Tuberculous Mycobacterial Diseases in Children.”

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Merck Manual (Consumer Version): “Infections Caused by Bacteria Related to Tuberculosis (TB).”

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American Lung Association: “Learn about NTM Lung Disease.”

Tuberculosis & Respiratory Diseases: “Treatment of Mycobacterium avium Complex Pulmonary Disease.”

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University of Notre Dame (College of Science): “Study sheds light on immune response in Mycobacterium avium Complex infection.”