Nontuberculous Mycobacteria Infections: Symptoms, Types, Causes and Treatment

Nontuberculous mycobacteria (NTM) infections are a growing public health concern worldwide, affecting people of all ages and backgrounds. Unlike tuberculosis, NTM infections arise from environmental mycobacteria, not person-to-person transmission. These infections can be challenging to diagnose and treat, often mimicking other diseases and requiring prolonged, complex therapy. In this article, we present a comprehensive, evidence-based overview of NTM infections—including their symptoms, types, causes, and current treatment approaches—so you can better understand this complex and increasingly common group of diseases.

Symptoms of Nontuberculous Mycobacteria Infections

Nontuberculous mycobacteria infections can present with a variety of symptoms depending on the site of infection and the underlying health status of the individual. The symptoms are often insidious and non-specific, overlapping with other respiratory or systemic diseases, which can delay diagnosis and treatment. Recognizing key clinical features is essential for early suspicion and intervention.

Symptom	Description	Common Sites	Source(s)
Chronic Cough	Persistent cough, often with sputum	Lungs	1 3 4
Weight Loss	Unintentional weight reduction	Systemic	1 3 4
Fatigue (Asthenia)	Generalized tiredness and lack of energy	Systemic	1 3
Dyspnoea	Shortness of breath	Lungs	1 3
Fever	Elevated temperature, sometimes low-grade	Systemic/Lungs	3 4
Skin Lesions	Nodules, abscesses, ulcers	Skin/Soft Tissue	5 6
Lymphadenopathy	Swollen lymph nodes (often cervical)	Lymph Nodes	3 4

Table 1: Key Symptoms

Pulmonary Symptoms

Most NTM infections affect the lungs, especially in individuals with underlying lung diseases or immunosuppression. The most common respiratory symptoms include:

• Chronic cough: Often with sputum that can be scant or purulent
• Dyspnoea (shortness of breath): May progress gradually
• Fatigue and malaise: Persistent tiredness is common
• Weight loss: Unintentional and gradual, sometimes severe
• Low-grade fever: Not always present, but can be a clue

These symptoms are similar to those of pulmonary tuberculosis, often making clinical distinction difficult without laboratory testing 1 3 4.

Extrapulmonary Symptoms

While the lungs are the primary site, NTM can also infect other parts of the body:

• Skin and Soft Tissues: After trauma or surgery, NTM can cause abscesses, ulcers, nodules, or non-healing wounds 5 6.
• Lymphadenitis: Especially in children, NTM may cause painless swelling of lymph nodes, particularly in the neck 3 4.
• Systemic Symptoms: In immunocompromised individuals, disseminated disease can result in fever, night sweats, and widespread organ involvement 3 6.

Variability by Patient Population

• Immunosuppressed patients are more likely to experience severe and disseminated symptoms.
• Patients with cystic fibrosis often have more persistent and severe pulmonary symptoms due to chronic infection, especially with Mycobacterium abscessus 2.

Types of Nontuberculous Mycobacteria Infections

NTM are a diverse group of organisms causing a range of clinical syndromes. The types of infections depend on the specific mycobacterial species, the site of infection, and patient risk factors.

Type	Main Characteristics	Common Species	Source(s)
Pulmonary Disease	Chronic cough, cavitary or nodular lung	MAC, M. abscessus	1 4 7 9
Skin/Soft Tissue	Abscesses, ulcers, nodules	M. marinum, M. abscessus, M. fortuitum	5 6 7
Lymphadenitis	Enlarged lymph nodes, often cervical	MAC, others	3 4 7
Disseminated Disease	Multi-organ involvement, fever	MAC, rapid growers	3 4 6 7

Table 2: Types of NTM Infections

Pulmonary NTM Disease

This is the most frequent form, particularly affecting:

• People with chronic lung conditions (COPD, bronchiectasis, cystic fibrosis)
• Elderly or immunosuppressed individuals

Key features:

• Chronic, slowly progressive symptoms
• Radiographic findings such as nodules, bronchiectasis, or cavities
• Most commonly caused by Mycobacterium avium complex (MAC) and M. abscessus 1 4 7 9

Skin and Soft Tissue Infections

NTM can invade through breaks in the skin after:

• Trauma (e.g., cuts, punctures)
• Surgery or cosmetic procedures

Characteristic features:

• Abscesses, nodules, non-healing ulcers
• Sporotrichoid spread (along lymphatic channels)
• Common causative species: M. marinum, M. abscessus, M. fortuitum, and M. chelonae 5 6 7

Lymphadenitis

• Primarily affects children, especially in the cervical (neck) lymph nodes
• Presents as painless, slowly enlarging lumps
• Often requires surgical excision for diagnosis and cure
• MAC is the most common cause 3 4 7

Disseminated Disease

Occurs mainly in severely immunocompromised patients (e.g., advanced HIV/AIDS, organ transplant recipients):

• Fever, weight loss, night sweats, and multi-organ involvement
• Blood cultures may be positive for MAC or rapid growers
• Requires urgent, aggressive treatment 3 4 6 7

Causes of Nontuberculous Mycobacteria Infections

NTM infections arise from environmental sources and are not transmitted person-to-person. Understanding the underlying causes can help with prevention and early detection.

Cause	Description	Risk Groups	Source(s)
Environmental	Soil, water, biofilms in plumbing	All, especially immunocomp.	10 7 8
Host Factors	Immunosuppression, lung disease	HIV/AIDS, CF, COPD, elderly	2 6 7
Trauma/Surgery	Skin barrier disruption	Surgical/trauma patients	5 6
Prior TB	Lung damage from prior TB	Individuals with TB history	9

Table 3: Causes of NTM Infections

Environmental Reservoirs

• NTM are ubiquitous in nature—found in soil, water (including drinking water), and dust 10.
• They colonize building water systems and form biofilms in plumbing, making exposure common 10 8.

Host Susceptibility

Certain host factors increase risk:

• Impaired immunity: Advanced HIV/AIDS, immunosuppressive therapy, organ transplantation 6 7
• Pre-existing lung disease: Chronic obstructive pulmonary disease (COPD), bronchiectasis, cystic fibrosis 2 7
• Elderly age: Age-related decline in immunity and lung function 4 7

Skin Barrier Disruption

• Infections commonly follow trauma, surgical procedures, or cosmetic interventions 5 6.
• Outbreaks have been associated with contaminated medical equipment and water sources in healthcare settings 5 6.

Prior Tuberculosis

• Individuals with a history of tuberculosis and residual lung damage are at increased risk for pulmonary NTM disease 9.

Geographic and Epidemiologic Factors

• Prevalence and species distribution vary by geographic region 9.
• In Asia, rapidly growing mycobacteria and a past TB history are notable risk factors 9.

Treatment of Nontuberculous Mycobacteria Infections

Managing NTM infections is notably challenging. Treatment regimens are often prolonged, require multiple drugs, and must be tailored to the specific species and patient profile. The need for specialized care and multidisciplinary management cannot be overstated.

Treatment	Approach/Drugs	Considerations	Source(s)
Antibiotics	Macrolides, rifamycins, ethambutol	Prolonged, multi-drug regimens	11 12 15
Susceptibility	Drug testing guides therapy	Essential for rapid growers	12 15
Surgery	Excision of infected tissue/nodes	Often for skin/lymphadenitis	5 6 11
Novel Therapies	Phage therapy, ongoing studies	For drug-resistant strains	14

Table 4: Treatment Approaches

Antibiotic Therapy

• Combination regimens are the standard, often including:
  • Macrolides (clarithromycin or azithromycin)
  • Rifamycins (rifampin or rifabutin)
  • Ethambutol
• Duration is typically 12 months or longer after culture conversion (negative cultures) 11 12 15.
• Regimens vary by species:
  • MAC: Macrolide-based triple therapy 11 12
  • M. abscessus: Extremely resistant; requires individualized therapy, often including intravenous agents 2 7 15
• M. kansasii and M. xenopi have distinct regimens 11

Susceptibility Testing

• Antimicrobial susceptibility testing is crucial, especially for rapidly growing NTM like M. abscessus, due to intrinsic resistance 12 15.
• Testing guides drug selection and helps avoid ineffective therapies 12 15.

Surgical Management

• Adjunctive surgery may be necessary in some cases:
  • Excision of localized skin/soft tissue infection 5 6
  • Resection of persistently infected lung tissue 11
  • Removal of infected catheters 6
• Surgery is also often required for NTM lymphadenitis in children 5 11

Management Considerations

• Treatment is prolonged and often difficult to tolerate due to drug toxicity, drug-drug interactions, and pill burden 15.
• Multidisciplinary care teams, including pharmacists and infectious disease specialists, improve outcomes 15.
• Monitoring for side effects and regular microbiological follow-up is essential 11 15.

Emerging and Adjunct Therapies

• Phage therapy: Early studies suggest that bacteriophages may help treat drug-resistant NTM (notably M. abscessus) when standard therapies fail. However, this approach is experimental and not widely available 14.
• Ongoing research is focused on new drugs, optimized regimens, and even vaccine development 8 14.

Special Populations

• Cystic fibrosis patients: Treatment is more challenging due to underlying disease and frequent co-infections; guidelines recommend following standard regimens with close monitoring 2 7 13.
• Immunocompromised patients: May require more aggressive and longer therapy, with attention to restoring immune function when possible 6 7.

Conclusion

Nontuberculous mycobacteria infections are complex, increasingly common, and require a nuanced, evidence-based approach for diagnosis and management. Key takeaways include:

• NTM infections present with non-specific symptoms that mimic other diseases, making clinical suspicion and laboratory confirmation essential.
• Pulmonary disease is most common, but NTM can also cause skin, soft tissue, lymph node, and disseminated infections.
• Environmental exposure and host susceptibility are critical factors in disease development; NTM are not transmitted person-to-person.
• Treatment is species-specific, prolonged, and challenging, often involving combination antibiotic regimens, susceptibility testing, and, in some cases, surgery or novel therapies.
• Research into improved diagnostics and treatments is ongoing, with phage therapy and new antibiotics offering promise for resistant cases.

Main Points Summary:

• NTM infections are rising globally and can affect various organ systems.
• Symptoms are diverse and often non-specific; prompt recognition is vital.
• Environmental exposure, underlying health, and trauma are key risk factors.
• Treatment requires prolonged, multi-drug regimens tailored to species and patient.
• Multidisciplinary care and ongoing research are central to improving outcomes.

Understanding NTM infections empowers patients and clinicians alike to seek timely diagnosis and appropriate care—crucial steps in tackling these challenging infections.