What is the initial treatment for non-tuberculosis mycobacterium (NTM) infections?

Initial Treatment for Non-Tuberculous Mycobacterial (NTM) Infections

The initial treatment for non-tuberculous mycobacterial (NTM) infections should be based on species identification and drug susceptibility testing rather than empiric therapy, with specific regimens tailored to the identified mycobacterial species. 1

Diagnostic Criteria Before Treatment

Before initiating treatment, confirm NTM disease using these criteria:

• Clinical symptoms (cough, fatigue, weight loss, fever)
• Radiographic findings (nodular/bronchiectatic pattern or cavitary disease)
• Microbiologic confirmation:
  • ≥2 positive sputum cultures, or
  • Positive culture from bronchial wash/lavage, or
  • Lung biopsy with histopathologic features and positive culture

Species-Specific Initial Treatment Regimens

1. Mycobacterium avium complex (MAC) - Most Common NTM

Nodular/Bronchiectatic Disease:

• Three-times-weekly regimen:
  • Azithromycin (500 mg) or clarithromycin (1,000 mg)
  • Rifampin (600 mg)
  • Ethambutol (25 mg/kg)

Fibrocavitary or Severe Disease:

• Daily regimen:
  • Azithromycin (250 mg) or clarithromycin (500-1,000 mg)
  • Rifampin (600 mg) or rifabutin (150-300 mg)
  • Ethambutol (15 mg/kg)
  • Consider adding amikacin or streptomycin three times weekly early in therapy 1

2. Mycobacterium kansasii

• Daily regimen:
  • Isoniazid (300 mg/day)
  • Rifampin (600 mg/day)
  • Ethambutol (15 mg/kg/day) 1

3. Mycobacterium abscessus

Initial Phase (4+ weeks):

• Intravenous therapy:
  • Amikacin plus
  • Tigecycline and/or imipenem and/or cefoxitin
• Oral therapy:
  • Macrolide (if susceptible)

Continuation Phase:

• Inhaled amikacin plus
• 2-4 oral antibiotics based on susceptibility:
  • Macrolide (if susceptible)
  • Clofazimine
  • Linezolid
  • Minocycline/doxycycline
  • Moxifloxacin/ciprofloxacin
  • Co-trimoxazole 1, 2

Drug Susceptibility Testing

• MAC: Test for macrolide and amikacin susceptibility
• M. kansasii: Test for rifampin susceptibility
• M. abscessus: Test for macrolide susceptibility (including 14-day incubation to detect inducible resistance) and amikacin 1

Treatment Duration

• Continue treatment for at least 12 months after sputum culture conversion for all NTM species 1

Important Considerations

• Never use macrolide monotherapy as it leads to resistance
• For severe disease with cavitation or positive acid-fast bacilli smears, initiate treatment promptly rather than watchful waiting
• Treatment success rates vary: 45-70% for MAC, with relapse rates up to 60% 3
• Adverse effects are common with NTM treatment regimens, requiring close monitoring
• Consider surgical resection for localized M. abscessus disease or treatment-refractory cases 1

Special Populations

• HIV/AIDS patients: For disseminated MAC, use clarithromycin (1,000 mg/day) or azithromycin (250 mg/day) plus ethambutol (15 mg/kg/day) with or without rifabutin (150-350 mg/day) 1
• Prophylaxis: For AIDS patients with CD4 <50 cells/μL, use azithromycin 1,200 mg weekly or clarithromycin 1,000 mg daily 1

Treatment of NTM infections is challenging due to long duration, potential toxicity, and variable response rates. Expert consultation is strongly recommended for management of these complex infections.