Mycobacterium abscessus infection

Mycobacterium abscessus complex is a challenging bacterial infection found in water, soil, and dust that can cause serious health problems, particularly in people with lung disease or weakened immune systems. Treatment is difficult and requires a combination of antibiotics for many months.

Table of contents

• What is Mycobacterium abscessus?
• Types of M. abscessus
• Signs and symptoms
• Who is at risk?
• How the infection spreads
• Diagnosis
• Treatment and recovery
• Reducing risk

What is Mycobacterium abscessus?

Mycobacterium abscessus complex is a type of bacteria that belongs to a group called nontuberculous mycobacteria (NTM), which are bacteria distantly related to those that cause tuberculosis and Hansen’s Disease (also known as Leprosy).^[1] Unlike tuberculosis bacteria, M. abscessus is found naturally in the environment—specifically in water, soil, and dust—and is considered an environmental mycobacterium.^[1]

This bacterium is classified as a rapidly growing mycobacterium, meaning it grows faster than other mycobacteria when cultured in a laboratory, typically within 3 to 7 days.^[4] M. abscessus is considered one of the most difficult infections to treat because it is naturally resistant to many commonly used antibiotics.^[2][4]

The bacteria can contaminate medications, medical products, and devices. It has been known to cause infections related to healthcare procedures as well as infections in people with certain underlying health conditions.^[1]

Types of M. abscessus

M. abscessus complex is divided into three main subspecies, which are important to identify because they respond differently to treatment.^[2][11] These subspecies include:

• M. abscessus subsp. abscessus – This is seen more commonly in North America. Many strains of this subspecies have a gene called erm(41) that can cause resistance to macrolide antibiotics, which are key drugs used in treatment.^[4]
• M. abscessus subsp. massiliense – This subspecies lacks the erm(41) resistance gene, which means it generally responds better to macrolide antibiotics. It is more frequently seen in Korea and other Asian countries.^[4]
• M. abscessus subsp. bolletii – This subspecies may have the resistance gene and is less commonly found in human infections.^[4]

Identifying which subspecies is causing an infection is critical for treatment decisions, as the presence or absence of the erm(41) gene affects how well macrolide antibiotics will work.^[11] Laboratory testing using molecular methods is needed to distinguish between these subspecies, as standard methods often cannot tell them apart.^[4]

Signs and symptoms

M. abscessus complex can cause a variety of infections affecting different parts of the body. The symptoms depend on where the infection occurs.^[2]

Common symptoms that may appear with any M. abscessus infection include:^[1]

• Fever
• Chills
• General feeling of illness
• Fatigue (extreme tiredness)
• Muscle aches

When M. abscessus infects the skin or soft tissues under the skin, symptoms may include:^[1]

• Boils or pus-filled blisters
• Skin that is red, warm, tender to the touch, swollen, or painful

When the bacteria cause lung infections, which are particularly common in people with chronic lung diseases such as cystic fibrosis, symptoms can include:^[1]

• Cough (sometimes with blood)
• Shortness of breath

M. abscessus can also cause infections in almost any part of the body, including the central nervous system, bloodstream, bones, lymph nodes, and eyes, though these are less common.^[2]

Who is at risk?

Not everyone who comes into contact with M. abscessus will develop an infection. However, certain groups of people are at higher risk.^[1]

People with open wounds are at risk of skin and soft tissue infections if M. abscessus bacteria from soil or water get into the wound.^[1] Healthcare-associated infections usually happen in the skin or tissues under the skin.^[1]

People with certain underlying health conditions face a higher risk of serious infections, particularly lung infections. These include individuals with:^[1]

• Chronic lung diseases such as cystic fibrosis, bronchiectasis (a condition where the airways are damaged and widened), asthma, or emphysema
• Weakened immune systems from conditions like HIV, cancer, or from taking medications that suppress the immune system

People who have medical devices that go into the body, such as central venous lines or breathing tubes, are also at increased risk of infection.^[1]

How the infection spreads

M. abscessus infections are not usually spread from person to person. Most people get infected through contact with the bacteria in the environment.^[1]

Common ways the infection spreads include:^[1]

• When soil or water containing M. abscessus bacteria gets into an open wound
• Through injections of substances that are contaminated with the bacteria
• During invasive medical procedures such as surgery, when contaminated equipment or materials are used

The bacteria can contaminate water systems, including those in healthcare facilities, as well as medical products and devices.^[1] Person-to-person transmission is not common, though it has been documented in rare cases.^[1]

Diagnosis

To diagnose an M. abscessus infection, healthcare providers will take a sample from the infected area and send it to a laboratory for testing.^[1] The type of sample depends on where the infection is located. For skin infections, a sample of infected tissue or pus may be collected. For lung infections, sputum (mucus coughed up from the lungs) is typically tested. Blood samples may also be taken.^[1]

The laboratory will culture the sample to grow and identify the bacteria. This process can take several days to weeks because mycobacteria grow more slowly than many other bacteria. Both solid and liquid culture media are used to increase the chances of detecting the bacteria.^[4]

Laboratory testing also includes susceptibility testing, which determines which antibiotics the bacteria are sensitive or resistant to. This information helps healthcare providers choose the right antibiotics for treatment.^[1] Molecular testing may be performed to identify which subspecies of M. abscessus is causing the infection and whether it has genes that cause antibiotic resistance.^[4]

Treatment and recovery

M. abscessus infections are extremely difficult to treat because the bacteria are naturally resistant to most antibiotics that are commonly used for skin or respiratory infections.^[1][7] Treatment requires a specialized approach and often lasts a long time.

Treatment typically involves two main components:^[1]

1. Surgical or drainage procedures – Draining pus or surgically removing infected tissue is often necessary, especially for skin and soft tissue infections.
2. Combination antibiotic therapy – Patients must take a combination of multiple antibiotics for an extended period, typically six months to one year or longer.^[1]

The antibiotics used are chosen based on laboratory susceptibility testing results. Treatment usually includes at least three active antibiotics used together.^[8] Common antibiotics that may be used include macrolides (such as clarithromycin or azithromycin), amikacin (given by injection or inhaled), cefoxitin, imipenem, and others.^[8]

One major challenge in treating M. abscessus is that many strains can develop resistance to macrolide antibiotics during treatment. This happens because of the erm(41) gene, which causes what is called inducible resistance—the bacteria become resistant after being exposed to the drug for a period of time, typically 3 to 14 days.^[4] Testing for this resistance mechanism is important and can help guide treatment decisions.^[4]

Side effects from the antibiotics are common and can be serious. Many patients experience problems that lead to changing medications or stopping treatment temporarily.^[7] Close monitoring by healthcare providers is essential throughout the treatment period.

For lung infections, frequent follow-up visits are recommended, and sputum cultures should be obtained every one to two months to check whether the treatment is working.^[16] Most patients who respond to treatment will have negative cultures within six months of starting antibiotics.^[16]

Reducing risk

While M. abscessus bacteria are common in the environment and cannot be completely avoided, there are steps that patients can take to reduce their risk of infection, especially when receiving healthcare.^[1]

Patients receiving healthcare should:^[1]

• Keep their hands clean by regularly washing with soap and water or using alcohol-based hand sanitizer, particularly before and after caring for wounds or touching medical devices
• Remind healthcare providers and others to clean their hands before touching them or handling medical devices
• Follow all instructions from healthcare providers before and after surgery or medical procedures
• Only receive medical care from licensed providers
• Inform their doctors if they think they have developed an infection after receiving medical care

Good infection control practices in healthcare settings can help reduce the risk of healthcare-associated M. abscessus infections.^[1]