Mycobacterium abscessus is a rapidly growing non-tuberculous mycobacteria (NTM) that has emerged as a significant public health concern. This bacterium can cause serious infections, particularly in individuals with pre-existing health conditions. While treatable, M. abscessus infections can lead to severe illness.
Understanding Mycobacterium Abscessus
Mycobacterium abscessus is an environmental bacterium found in water, soil, and dust. It belongs to non-tuberculous mycobacteria (NTM), distinct from Mycobacterium tuberculosis (which causes tuberculosis). Unlike M. tuberculosis, NTM species like M. abscessus are not typically transmitted person-to-person and have environmental reservoirs.
It has been reclassified as Mycobacteroides abscessus but is still commonly referred to by its former name. M. abscessus is further divided into three subspecies: M. abscessus subsp. abscessus, M. abscessus subsp. massiliense, and M. abscessus subsp. bolletii. These subspecies can vary in their drug susceptibility and potential for transmission.
How Infection Occurs
Infection with Mycobacterium abscessus primarily results from environmental exposure rather than person-to-person spread. The bacterium can enter the human body through various pathways, most commonly through contaminated water sources. This includes exposure via tap water, medical devices that use non-sterile water, or improperly sterilized surgical instruments.
Entry points for the bacteria can include breaks in the skin, such as surgical sites or open wounds. Inhalation of aerosols containing the bacteria, for instance from showerheads, can also lead to infection, particularly in the lungs.
Recognizing Symptoms and Diagnosis
M. abscessus infections can cause various symptoms in different body parts. Skin and soft tissue infections are common, presenting as boils, pus-filled blisters, redness, warmth, tenderness, swelling, and pain. These can occur after surgery, injections, or exposure to contaminated environments like hot tubs.
Lung infections are also common, especially in individuals with pre-existing lung conditions such as cystic fibrosis or bronchiectasis. Symptoms of pulmonary infection can include chronic cough, often with purulent sputum, and sometimes hemoptysis. Systemic symptoms like fever, chills, muscle aches, and a general feeling of illness may also occur.
Diagnosing M. abscessus infection can be challenging due to non-specific symptoms that mimic other conditions. Diagnosis typically involves culturing the organism from the infected site, such as pus, biopsy tissue, or sputum, and in severe cases, from blood samples. Molecular tests can further identify the specific subspecies, which is important for guiding treatment.
Challenges in Treatment
Treating M. abscessus infections is difficult due to several factors. The bacterium exhibits intrinsic resistance to many common antibiotics, making it difficult to manage. This resistance necessitates the use of multi-drug regimens, often involving a combination of intravenous and oral antibiotics.
Treatment durations are typically long, ranging from several months to over a year. Another obstacle is the bacterium’s ability to form biofilms, which are protective communities of bacteria encased in a matrix. Biofilms act as a physical barrier, reducing antibiotic penetration and making bacteria more tolerant to treatment and immune responses. Additionally, the powerful antibiotics used can cause significant side effects, impacting patient adherence and overall outcome. For localized infections, surgical removal of infected tissue or drainage of pus is often performed in conjunction with antibiotic therapy to improve treatment success.
Outcomes and Mortality
While not universally fatal, M. abscessus infection can lead to serious illness and, in some cases, death, particularly in vulnerable populations. Factors influencing the outcome include the site of infection and the patient’s underlying health status. Disseminated infections, where the bacteria spread throughout the body, are generally more severe than localized ones.
Individuals who are immunocompromised or have severe pre-existing lung diseases, such as cystic fibrosis or chronic obstructive pulmonary disease, face a higher risk of adverse outcomes. The specific subspecies of M. abscessus and its resistance patterns also play a role in prognosis; for example, M. abscessus subsp. abscessus is often more resistant to macrolides and difficult to treat compared to M. abscessus subsp. massiliense. Mortality rates vary depending on the patient group and the severity of the disease. For instance, studies have shown 5-year cumulative mortality rates for pulmonary M. abscessus disease around 11.4%, increasing to 50.6% at 15 years. Early diagnosis and aggressive, long-term treatment are important for improving patient outcomes and reducing severe consequences.