What Are Nontuberculous Mycobacteria Infections

Bacteria are found in many environments and locations, including soil, ocean water, human skin, and the digestive tract. Currently, it is estimated that over 5% of bacterial species are capable of causing infections in humans. Some of them are recognized as being pathogenic to humans in recent research. Nontuberculous mycobacteria (NTM) is one of them. So, what is known about this pathogen, and what are nontuberculous infections?

Nontuberculous mycobacteria have a long history of being considered contaminants, although their clinical significance has often been overlooked. Nontuberculous mycobacteria were not recognized as a cause of human disease until the 1930s. Before that, they were thought to be benign organisms that were commonly found in the environment. 

However, as medical knowledge and techniques for identifying different species of bacteria improved, it became clear that certain species of NTM could cause severe infections in humans, particularly in people with underlying lung conditions such as silicosis. The first case of NTM lung disease was reported in 1943 in a man with silicosis.

NTM infections have been increasing in recent decades, and pulmonary disease is the most common manifestation of these infections. Immunocompromised people with underlying lung diseases or conditions that weaken the immune system are particularly susceptible to NTM lung infections. This increase in NTM infections is likely due to a combination of factors, including an 

• ageing population
• increasing use of immunosuppressive drugs
• and improved diagnostic techniques that make identifying and detecting NTM infection easier

Overview

Nontuberculous mycobacterium (NTM) is a group of opportunistic bacteria that can cause infections in humans, animals, and birds. These infections can affect various body sites, including the skin, lymph nodes, and lungs, and they often have a chronic course with slow progression. Diagnosing NTM infections can be challenging as they often resemble other illnesses and may require specialized laboratory tests for confirmation. 

Treatment of NTM infection is often prolonged and requires the use of multiple antibiotics. The virulence of NTM, the site of infection, and the presence of underlying medical conditions can all impact the outcome. 

Causes of nontuberculous mycobacteria infections

The exposure of individuals to environmental sources of NTM, such as water, soil, and air, can all cause infection. The exact way NTM infects an individual can vary. It often involves cuts or breaks in the skin, penetrating trauma, contaminated wounds, or inhalation of NTT into the lungs. The NTM infection can also occur through injection of intravenous and peritoneal catheters, shunts, intramuscular injections, cosmetic surgery procedures, laser in situ keratomileusis procedures, and postsurgical wounds.

Signs and symptoms of nontuberculous mycobacteria infections

Nontuberculous mycobacteria species include slow-growing Mycobacterium avium complex (MAC) and fast-growing species such as Mycolicibacterium fortuitum and Mycobacteroides abscesses. The NTM group encompasses tens of bacterial species, each with unique characteristics and features.

The signs and symptoms of NTM infections can vary depending on the site of infection, but they may include:

Skin, soft tissue, and skeletal infections

Redness, swelling, pain, and/or the formation of abscesses or nodules at the site of infection. Mycobacterium ulcerans, mycobacterium fortuitum, and mycobacterium abscessus of the NTM bacteria group mainly cause skin or soft tissue infection.

Pulmonary NTM

Chronic cough is nearly universal in these cases, but other symptoms such as fever, malaise, weight loss, shortness of breath, and hemoptysis may also occur. Pulmonary NTM is often associated with mycobacterium avium complex and abscessus complex.

Disseminated disease

Which is primarily found in patients with advanced HIV disease and manifests through fever, night sweats, weight loss, fatigue, and/or muscle and joint pain, sometimes diarrhoea and abdominal pain. 

Lymph node infection 

It is the most common presentation of NTM disease in children, with the head and neck region being the most commonly affected area. The typical presentation of NTM infection in lymph nodes is a painless swelling of one or more lymph nodes.

Mycobacterial infection can slow progress, and the symptoms may be subtle, making them difficult to diagnose. It is essential to seek medical attention if you experience any persistent or worsening symptoms, especially if you have underlying medical conditions or have been exposed to environmental sources of infectious disease. Early diagnosis and treatment of NTM infection can improve the outcome and prevent the spread of bacteria to others.

Management and treatment for nontuberculous mycobacteria infections

Treatment of NTM infection typically involves using antibiotics, often multiple antibiotics, to sterilize the infection. The choice of antibiotics, therapy duration, and treatment response can vary depending on the site of infection, the specific NTM species involved, and the presence of underlying medical conditions. 

In addition to antibiotics, other measures that may be used to manage infections caused by NTM include surgical intervention, such as the drainage of abscesses or removal of infected tissue.

It is essential to work closely with a healthcare provider who can monitor the response to treatment and adjust therapy as needed. In some cases, NTM infections can be persistent and may require prolonged treatment, and some infections may not respond to therapy.

In addition to specific therapy for NTM infection, it is essential to address underlying medical conditions that can increase the risk of NTM infections and to take steps to prevent exposure to environmental sources of NTM infection.

FAQs

How are nontuberculous mycobacteria infections diagnosed?

The following are some of the critical steps in diagnosing NTM infections:

1. The clinical evaluation assesses the signs and symptoms of infection and identifies any underlying medical conditions that may increase the risk of NTM infection
2. Microbiological testing: Specimens from the site of infection, such as sputum, blood, or biopsy material, are collected and tested for the presence of NTM. This typically involves culturing the specimen on special media to promote the growth of NTM and using molecular techniques to identify the specific NTM species involved
3. Imaging studies, such as chest X-ray or computed tomography (CT) scans, may be used to assess the extent of lung involvement and to identify other areas of the body that may be affected by NTM infection

A definitive diagnosis of NTM infection requires laboratory confirmation of the presence of NTM in the specimen and identification of the specific NTM species involved. In some cases, additional tests, such as drug susceptibility testing, may be performed to guide treatment decisions.

How can I prevent nontuberculous mycobacteria infections?

Since 2021, there have been no recommended vaccination protocols or established preclinical models to study the efficacy of potential vaccines against the many different types of nontuberculous mycobacteria (NTM). Further research and development are needed in this area. 

There are several steps you can take to reduce your risk of NTM infection:

Maintain good hygiene

Regular hand washing, especially after being in contact with soil or water, and avoiding exposure to contaminated water sources can help prevent nontuberculous mycobacterial infection.

Practice safe water activities

Avoid swallowing water while swimming in natural bodies of water and exposing open wounds to contaminated water.

Address underlying medical conditions

Conditions such as weakened immune systems, chronic lung disease, and skin conditions can increase the risk of NTM infection. It is essential to work with a healthcare provider to manage these conditions and to take steps to reduce the risk of NTM infection.

Be mindful of medical procedures

NTM infections can occur following procedures, such as surgery or injection, that involve introducing contaminated material into the body. Be sure to discuss any concerns with your healthcare provider and take steps to reduce the risk of exposure to contaminated materials.

Avoid exposure to contaminated dust and soil

NTM bacteria are widely distributed in the environment and can be found in contaminated dust and soil. Avoid exposure to contaminated dust and soil, and wear appropriate personal protective equipment, such as masks, when working in dusty environments.

Early diagnosis, treatment of NTM infections, and disease control are essential to reduce the risk of severe complications and prevent the spread of NTM to others.

Who is at risk of nontuberculous mycobacteria infections?

Anyone can be at risk of nontuberculous mycobacterial disease, but some individuals are more susceptible due to underlying medical conditions or environmental exposures.

1. People with weakened immune systems. Individuals with conditions such as HIV/AIDS, organ transplant recipients, and those undergoing chemotherapy are at increased risk of nontuberculous mycobacterial disease due to weakened immune systems
2. People with certain lung conditions, such as chronic obstructive pulmonary disease (COPD), cystic fibrosis, bronchiectasis, or have a history of mycobacterium tuberculosis infection
3. People who have had recent medical procedures, such as joint replacements, or have received injections or other medical procedures that introduce contaminated material into the body are at increased risk of NTM infections
4. People who have frequent exposure to contaminated water or soil: Individuals who work in environments with contaminated water or soil, such as farmers, construction workers, and gardeners
5. People with skin conditions, such as eczema or dermatitis

It is essential to work with a healthcare provider to assess your risk of NTM infection and to take steps to reduce your risk, such as practising good hygiene and avoiding exposure to contaminated environments.

When should I see a doctor?

You should see a doctor if you experience any symptoms that may be indicative of an NTM infection, such as:

1. Persistent or worsening respiratory symptoms, such as coughing, shortness of breath, chest pain, or wheezing
2. Skin lesions, such as bumps, lumps, or red or painful areas that do not heal
3. Persistent fever, night sweats, or weight loss
4. Swelling or pain in joints
5. Drainage from a surgical wound

Your doctor can perform tests to determine if you have an NTM infection and develop an appropriate treatment plan.

Summary

Nontuberculous mycobacteria (NTM) are a diverse group of microorganisms that can cause many human diseases, from minor, self-limited skin infections to life-threatening, widespread conditions that may not have effective therapy. In the past, NTM was thought to only affect immunocompromised individuals, but they are now recognized as a significant cause of disease in immunocompetent individuals. 

Diagnosing NTM infections involves a combination of clinical features, microbiological data, radiographic findings, and histopathologic studies. Treatment of NTM infections can be challenging and often requires long courses of multidrug therapy, sometimes combined with adjunctive surgical interventions. Due to the diversity of NTM species and the wide range of diseases they can cause, it is essential for healthcare providers to have a thorough understanding of these infections and to be able to recognize and diagnose them accurately and promptly.