Mycobacterium abscessus infection is caused by bacteria found naturally in our environment that can lead to serious health problems, particularly affecting the lungs, skin, and soft tissues. These infections are notoriously difficult to treat due to the bacterium’s resistance to many common antibiotics, requiring lengthy treatment with multiple medications.

What Is Mycobacterium Abscessus?

Mycobacterium abscessus complex is a type of bacterium that belongs to a larger group of environmental bacteria known as nontuberculous mycobacteria (NTM). While it is distantly related to the bacteria that cause tuberculosis and Hansen’s Disease, also known as leprosy, it behaves very differently from these better-known conditions. The bacterium gets its name from the Latin word for abscess, as it was first discovered in a patient who developed multiple abscesses throughout her body.^[1]

This bacterium is commonly found in water, soil, and dust around us. It lives naturally in the environment and has been discovered contaminating various products and medical devices. Despite being all around us, most people who come into contact with these bacteria never develop an infection. The bacterium becomes problematic primarily when it enters the body through wounds, contaminated medical equipment, or when it is inhaled by people with underlying health conditions.^[2]

Mycobacterium abscessus is classified as a rapidly growing mycobacterium, meaning it grows faster in laboratory cultures compared to other mycobacteria like those causing tuberculosis. Despite this “rapid” classification, it still takes several days to grow on laboratory plates, typically between three to seven days. The bacterium is also considered one of the most resistant to treatment among all the rapidly growing mycobacteria, making infections particularly challenging for both patients and healthcare providers.^[3]

There are three main subspecies of Mycobacterium abscessus that can cause disease in humans. These include Mycobacterium abscessus subspecies abscessus, Mycobacterium abscessus subspecies massiliense, and Mycobacterium abscessus subspecies bolletii. Identifying which subspecies is causing an infection is important because they respond differently to treatment, particularly to a class of antibiotics called macrolides.^[4]

Epidemiology

Infections caused by nontuberculous mycobacteria, including Mycobacterium abscessus, have been increasing around the world over the past decade. This rise in cases has been documented across many countries, though the exact reasons for this increase are not fully understood. It may be due to better detection methods, increased awareness among healthcare providers, or genuine increases in environmental exposure.^[8]

Among nontuberculous mycobacterial lung infections, Mycobacterium abscessus is the second most common cause of disease. The most common subspecies causing human infections are Mycobacterium abscessus subspecies abscessus and Mycobacterium abscessus subspecies massiliense. In North America, subspecies abscessus tends to be seen more frequently, while subspecies massiliense appears more commonly in countries like Korea.^[4]

Certain groups of people are more likely to develop Mycobacterium abscessus infections. Women with low body mass index and certain underlying health conditions appear to be at higher risk for developing lung infections from this bacterium. This pattern is particularly notable in patients with chronic lung conditions. Among people with cystic fibrosis, a genetic condition that causes thick mucus to build up in the lungs, Mycobacterium abscessus represents one of the most serious infectious threats and can significantly impact their health and survival, especially for those awaiting or having undergone lung transplantation.^[2][14]

Causes and How Infection Spreads

Mycobacterium abscessus infections develop when bacteria from the environment enter the body and establish an infection. Since these bacteria live naturally in water, soil, and dust, exposure to contaminated environmental sources represents the primary route of infection. The bacteria do not normally spread from person to person, which means most infections are acquired from environmental sources rather than from contact with infected individuals.^[1]

One common way people acquire these infections is through contaminated water sources. Activities like bathing, showering, or even drinking water that contains Mycobacterium abscessus can lead to exposure. For lung infections specifically, inhaling tiny droplets of water containing the bacteria, such as from showers or humidifiers, can introduce the organism into the respiratory system. This is particularly problematic for people who already have damaged or diseased lungs, as the bacteria can more easily establish infection in compromised tissue.^[17]

Healthcare-associated infections represent another important route of transmission. These infections typically occur in the skin or soft tissues beneath the skin and can happen through several mechanisms. Injections of substances contaminated with Mycobacterium abscessus bacteria can introduce the organism directly into tissues. Invasive medical procedures, including surgeries performed with contaminated equipment or materials, can also lead to infection. Medical devices like central venous lines, breathing tubes, or feeding tubes that go into the body can serve as pathways for bacteria to enter.^[1]

Wounds that come into contact with soil or water containing these bacteria can become infected. This might happen after injuries outdoors, during cosmetic procedures performed in non-sterile conditions, or through contaminated needles used for tattooing or drug injection. The bacteria are particularly good at surviving on surfaces and can contaminate medications and medical products if proper sterilization procedures are not followed.^[2]

Risk Factors

Several factors increase a person’s likelihood of developing a Mycobacterium abscessus infection. Understanding these risk factors helps identify individuals who need to be particularly careful about exposure and who should be monitored closely if they develop symptoms. People with open wounds are at increased risk because the bacteria can enter the body through breaks in the skin. This is especially concerning if wounds come into contact with potentially contaminated water or soil.^[1]

Underlying respiratory conditions significantly increase the risk of developing lung infections from Mycobacterium abscessus. Conditions such as cystic fibrosis, bronchiectasis (a condition where the airways become damaged and widened), asthma, and emphysema all make the lungs more vulnerable to infection. In these conditions, the normal defense mechanisms of the lungs are impaired, making it easier for bacteria to establish infection and more difficult for the body to clear them.^[17]

People with weakened immune systems face substantially higher risk for both acquiring infections and developing more severe disease. This includes individuals with HIV infection, cancer, or other conditions that compromise immune function. Those taking immunosuppressive medications, such as drugs given after organ transplantation or medications for autoimmune conditions, are also more vulnerable to infection. When the immune system cannot function properly, it becomes much harder to fight off bacteria that a healthy immune system might easily control.^[1]

Certain demographic and physical factors also play a role. Women appear to be at higher risk than men for some types of Mycobacterium abscessus infections, particularly lung disease. Having a low body mass index increases risk, as does having certain conditions affecting the chest structure like scoliosis (curvature of the spine) or pectus excavatum (sunken chest). People with mitral valve prolapse, a heart valve condition, or chronic acid reflux disease known as GERD, also face elevated risk.^[17]

Medical devices and procedures that penetrate the body create potential entry points for bacteria. Having a central venous line, which is a tube inserted into a large vein for medication delivery, increases risk. Similarly, breathing tubes, feeding tubes, or other devices that go into the body can serve as pathways for infection. Receiving medical care from unlicensed providers or in settings that do not follow proper sterilization procedures substantially increases the risk of acquiring a healthcare-associated infection.^[1]

Symptoms

The symptoms of Mycobacterium abscessus infection vary depending on where in the body the bacteria are causing disease. Many symptoms are not specific to this particular infection, meaning they can look similar to other conditions, which sometimes makes diagnosis challenging. Understanding the range of possible symptoms helps patients recognize when they might have an infection and need medical evaluation.^[1]

Several general symptoms can occur regardless of the infection site. These include fever, which may come and go or persist over time. Many patients experience chills, particularly when fever is present. A general feeling of illness or unwellness, sometimes described as malaise, is common. Muscle aches can develop throughout the body. Some people experience significant fatigue and unintended weight loss, particularly when infection has been present for some time.^[1]

When Mycobacterium abscessus infects the skin or soft tissues, specific local symptoms develop at the infection site. The skin may become red, warm to the touch, tender, swollen, and painful. Boils or pus-filled blisters can form. Some infections develop into abscesses, which are collections of pus beneath the skin. These skin and soft tissue infections are the most common type seen in healthcare-associated cases and can occur anywhere on the body where bacteria were introduced.^[1]

Lung infections produce respiratory symptoms that significantly impact quality of life. A persistent cough is one of the most common symptoms, and this cough may produce sputum or mucus. In some cases, the sputum may contain blood, which is always a concerning sign that requires medical attention. Patients often experience shortness of breath, which may worsen over time as the infection progresses. The chronic nature of these lung infections means symptoms often persist for weeks or months before diagnosis.^[17]

When bones or joints are infected, patients typically experience pain and stiffness in the affected areas. These musculoskeletal infections are less common than skin or lung infections but can be quite serious. If lymph nodes become infected or swollen in response to infection elsewhere in the body, they may be felt as lumps under the skin, most commonly in the neck, armpits, or groin.^[17]

Prevention

Preventing Mycobacterium abscessus infection involves reducing exposure to bacteria and taking precautions to prevent contamination, particularly in healthcare settings. While it is impossible to completely avoid environmental exposure to these bacteria since they are found naturally in water and soil, several practical measures can reduce infection risk.^[1]

Good hand hygiene represents one of the most important preventive measures. Regularly washing hands with soap and water or using alcohol-based hand sanitizer helps remove bacteria that may have been picked up from the environment. This is particularly important before and after caring for wounds or touching any medical device that enters the body. Patients should not hesitate to remind healthcare providers and visitors to clean their hands before touching them or handling medical equipment.^[1]

Following all healthcare provider instructions carefully before and after any surgery or medical procedure helps minimize infection risk. This includes wound care instructions, which should be followed precisely to keep surgical sites or other wounds clean and protected from environmental contamination. Only receiving medical care from licensed providers who follow proper infection control practices and sterilization procedures is crucial. This applies not just to hospitals and clinics, but also to facilities offering cosmetic procedures, tattooing, or other services involving needles or equipment that penetrates the skin.^[1]

For people with chronic lung conditions who are at higher risk for lung infections, measures to reduce inhalation of contaminated water droplets may be helpful. This might include being cautious with humidifiers, hot tubs, and shower heads, ensuring they are properly maintained and cleaned. Some experts suggest that people at very high risk might consider using water filters or taking other precautions with their water sources, though specific recommendations should come from healthcare providers familiar with the individual patient’s situation.^[17]

Patients receiving healthcare should be alert to signs of infection after any medical procedure. If symptoms such as fever, unusual pain, redness, swelling, or drainage develop after surgery or other invasive procedures, it is important to notify healthcare providers promptly. Early detection and treatment of infections generally leads to better outcomes. Advocating for good infection control practices in healthcare settings, including proper sterilization of equipment and appropriate use of sterile techniques during procedures, benefits everyone.^[1]

Pathophysiology

Understanding what happens in the body during a Mycobacterium abscessus infection helps explain why these infections are so difficult to treat and why they cause the symptoms they do. The pathophysiology refers to the changes that occur in normal body functions when disease is present. In the case of Mycobacterium abscessus infection, several unique characteristics of the bacteria contribute to its ability to cause persistent infection.^[2]

Mycobacterium abscessus is classified as multidrug-resistant, meaning it is naturally resistant to many antibiotics that would normally kill bacteria. This resistance is not due to prior exposure to antibiotics, but rather is an inherent characteristic of the organism. The bacterium produces substances called beta-lactamases, which are enzymes that break down certain common antibiotics before they can work. This makes many standard antibiotics ineffective against Mycobacterium abscessus from the start.^[2]

The bacteria have a thick, waxy coating on their outer surface that makes them particularly hardy and resistant to many environmental stresses and antimicrobial agents. This coating also makes them acid-fast, which is a laboratory characteristic that helps identify them under a microscope using special staining techniques. The waxy coating protects the bacteria from many of the body’s natural defenses and from antibiotics trying to penetrate and kill them.^[3]

When Mycobacterium abscessus infects the lungs, it typically establishes chronic infection in areas of already damaged lung tissue. The bacteria can form structures called biofilms, which are communities of bacteria encased in a protective matrix that makes them even more resistant to both antibiotics and immune system attacks. Within biofilms, bacteria communicate with each other and can survive in a dormant state that makes them particularly difficult to eradicate with antibiotics that primarily work on actively growing bacteria.^[14]

The immune system responds to the presence of Mycobacterium abscessus by sending various immune cells to the infection site. However, these bacteria have evolved ways to survive even inside immune cells called macrophages, which normally engulf and destroy bacteria. By surviving within these cells, the bacteria evade many immune defenses and can persist for long periods. The ongoing immune response to the infection causes inflammation, which damages surrounding healthy tissue and contributes to symptoms and progressive disease.^[14]

Different subspecies of Mycobacterium abscessus have different genetic profiles that affect treatment response. Some subspecies possess a gene called erm(41) that can be activated when exposed to certain antibiotics, particularly macrolides. When this gene is functional and gets turned on, it causes the bacteria to become resistant to macrolides even though they may have initially been susceptible. This inducible resistance can develop during treatment, which is why antibiotics that initially seemed to be working may lose effectiveness over time. Subspecies massiliense typically lacks a functional erm gene, which is why infections with this subspecies often respond better to macrolide-containing treatment regimens.^[4]

In skin and soft tissue infections, the bacteria cause local inflammation and can lead to abscess formation. The immune system attempts to wall off the infection, creating pockets of pus that contain bacteria, dead immune cells, and tissue debris. While this response helps prevent spread, it also creates an environment where antibiotics have difficulty penetrating, making these infections resistant to antibiotic therapy alone and often requiring surgical drainage or removal of infected tissue for successful treatment.^[1]