Treatment Guidelines for Nontuberculous Mycobacteria (NTM) Infections
Treatment of NTM pulmonary disease should be initiated based on species identification and drug susceptibility testing rather than empiric therapy, especially for MAC, M. kansasii, and M. abscessus infections. 1
Diagnosis of NTM Pulmonary Disease
Before initiating treatment, proper diagnosis is essential using the ATS/IDSA criteria:
Clinical and Microbiologic Criteria
- Clinical symptoms: Pulmonary or systemic symptoms
- Radiologic findings: Nodular or cavitary opacities on chest radiograph, or HRCT showing bronchiectasis with multiple small nodules
- Microbiologic confirmation:
- Positive culture results from ≥2 separate expectorated sputum samples, OR
- Positive culture from at least one bronchial wash/lavage, OR
- Lung biopsy with mycobacterial histologic features and positive NTM culture 1
Important Considerations
- The pathogenicity varies significantly between NTM species (M. gordonae rarely causes disease, while M. kansasii is typically pathogenic)
- Meeting diagnostic criteria doesn't automatically necessitate treatment - clinical judgment is required 1
- For low pathogenicity species, multiple positive cultures over months are needed, while a single positive M. kansasii culture may justify treatment 1
Treatment Recommendations by Species
1. Mycobacterium avium complex (MAC)
Recommended regimen:
- Daily oral macrolide (preferably azithromycin)
- Rifampin
- Ethambutol 1
- Consider initial course of IV amikacin for severe disease 1
Key points:
- Macrolide susceptibility testing is essential 1
- Never use macrolide monotherapy (leads to resistance) 1
- Treat for at least 12 months after sputum culture conversion 2, 3
- Intermittent (three times weekly) therapy is not recommended 1
2. Mycobacterium abscessus Complex
Recommended regimen:
Intensive phase (3-12 weeks):
- Daily oral macrolide (preferably azithromycin)
- IV amikacin
- Plus one or more: IV tigecycline, imipenem, or cefoxitin 1
Continuation phase:
- Daily oral macrolide
- Inhaled amikacin
- Plus 2-3 of: minocycline, clofazimine, moxifloxacin, linezolid 1
Key points:
- For macrolides, 14-day incubation and/or sequencing of erm(41) gene is required to evaluate for inducible resistance 1
- Treatment is difficult, requiring long-term parenteral agents 3
- M. massiliense responds better to treatment than M. abscessus 3
- Expert consultation is strongly recommended due to frequent drug intolerance and toxicity 1
3. Mycobacterium kansasii
Recommended regimen:
- Isoniazid
- Rifampin (susceptibility testing essential)
- Ethambutol 2
Key points:
- Often endemic in cities with infected tap water 2
- Clinical presentation resembles tuberculosis 2
- Generally more responsive to treatment than other NTM species 1
Treatment Duration and Monitoring
- Continue treatment for at least 12 months after sputum culture conversion 2, 3, 4
- Use at least three drugs to minimize development of resistance 4
- Regular sputum cultures to monitor response
- Monitor for drug toxicity, especially with long-term use
Special Populations
Cystic Fibrosis Patients
- More aggressive treatment approach may be needed
- Person-to-person transmission of M. abscessus can occur in this population 5
- Discontinue azithromycin maintenance therapy during NTM evaluation to prevent resistance 1
Treatment Challenges
- NTM treatment is longer than TB treatment
- Higher likelihood of treatment failure and drug toxicity 4
- Underlying lung diseases complicate management
- Drug intolerance is common, especially with prolonged therapy
Surgical Management
- Reserved for localized disease with good pulmonary function 5
- Consider in cases of treatment failure or severe localized disease
NTM pulmonary disease treatment requires a long-term commitment with careful monitoring for both treatment response and adverse effects. Species identification and susceptibility testing are crucial for optimizing treatment outcomes.