Pulmonary non-tuberculous mycobacterial infection

Pulmonary non-tuberculous mycobacterial (NTM) infection refers to pulmonary infection caused by one of the large number (at least 150) mycobacterial species other than Mycobacterium tuberculosis. However, certain species are much more common than others.

Epidemiology

Risk factors

• chronic lung diseases such as ¹²:
  • asthma
  • COPD
  • alpha-1 antitrypsin deficiency
  • cystic fibrosis (CF)
  • pneumoconioses
  • non-CF bronchiectasis
  • primary ciliary dyskinesia
  • allergic bronchopulmonary aspergillosis
• older age and tall slim white females seem to be more susceptible
• immunodeficiency states ¹²
  • inherited disorders of IFNγ-IL12 pathway (e.g. IFNγR1 mutations)
  • other cytokine signalling disorders (e.g. STAT mutations)
  • macrophage and dendritic cell function disorders (e.g. GATA2 and NRAMP)
  • acquired immunodeficiencies (HIV-AIDS)
  • functional anti-interferon gamma antibodies
• gastro-oesophageal reflux disease (GORD)

Associations

There may be an association between achalasia of the gastric cardia and M. fortuitum/chelonae infection.

Clinical presentation

Some patients are relatively asymptomatic. However, most have a combination of respiratory and systemic features that may resemble pulmonary tuberculosis:

• chronic cough
• shortness of breath on exertion
• haemoptysis
• low grade fever
• night sweats
• fatigue
• weight loss

Pathology

As with M. tuberculosis, non-tuberculous mycobacteria (NTM) commonly cause pulmonary infection. More than 150 species of NTM species have been identified some of which can cause infections in humans. These include:

• Mycobacterium avium-intracellulare (MAI): ~60% (on bronchial secretions)
  • see: pulmonary MAIC infection
• Mycobacterium kansasii: ~25%
• Mycobacterium fortuitum
• Mycobacterium malmoense: pulmonary Mycobacterium malmoense infection
• Mycobacterium gordonae
• Mycobacterium szulgai
• Mycobacterium scrofulaceum / Mycobacterium parascrofulaceum: pulmonary Mycobacterium parascrofulaceum infection
• Mycobacterium xenopi
• Mycobacterium chelonae: pulmonary Mycobacterium chelonae infection
• Mycobacterium chimerae: pulmonary Mycobacterium chimerae infection
• Mycobacterium simiae
• Mycobacterium palustre
• Mycobacterium kumamotonense
• Mycobacterium kubicae
• Mycobacterium morokaense
• Mycobacterium abscessus: pulmonary Mycobacterium abscessus infection ²

Treatment and prognosis

Detailed guidelines on the management approach are available ¹².The general principles are:

• multidrug therapy according to the sensitivities of the organisms
• treatment for at least 12 months
• specialist follow-up to monitor compliance and drug side-effects