From the Guidelines
The diagnosis and treatment of non-tuberculous mycobacterial (NTM) infections requires a multifaceted approach combining clinical, radiological, and microbiological evidence, with treatment depending on the specific NTM species identified and guided by the most recent clinical practice guidelines 1. The approach to diagnosis involves collecting appropriate respiratory specimens (sputum, bronchial wash, or lung tissue) for acid-fast bacilli smear, culture, and species identification, with multiple positive cultures with the same NTM species typically required to distinguish colonization from true infection 1. Key considerations in diagnosis include:
- Positive culture results from at least two separate expectorated sputum samples
- Positive culture results from at least one bronchial wash or lavage
- Transbronchial or other lung biopsy with mycobacterial histopathologic features and positive culture for NTM Treatment depends on the specific NTM species identified, with Mycobacterium avium complex (MAC) being the most common, and for MAC pulmonary disease, the standard regimen includes a macrolide, ethambutol, and rifampin, continuing for 12 months after culture conversion 1. For other NTM species such as M. abscessus, different regimens are often required, including combinations of macrolides, amikacin, imipenem, tigecycline, and other antibiotics based on susceptibility testing 1. Treatment success requires regular monitoring of sputum cultures, medication side effects, and adherence support, with expert consultation helpful in many settings 1. Given the complexity of NTM treatment, including natural antibiotic resistance, biofilm formation capabilities, and the ability to persist within macrophages, prolonged multidrug therapy is often necessary to achieve cure, and the most recent guidelines should be consulted for specific treatment recommendations 1.
From the Research
Diagnosis of Non-Tuberculous Mycobacterial (NTM) Tuberculosis
- The clinical presentation for most NTM infections is non-specific, often resulting in delayed diagnosis 2.
- Diagnosis may be difficult, especially in AIDS patients in whom numerous diseases are often associated 3.
- Diagnostic criteria involve clinical, radiological, microbiological and pathological findings 3.
- Identification of Mycobacterium species in cultures is the gold standard 3.
- The development of molecular methods allows the characterization of new species and NTM identification at a subspecies level 4.
Treatment of Non-Tuberculous Mycobacterial (NTM) Tuberculosis
- Medications used to treat NTM infection can be difficult for patients to tolerate, and prolonged courses of anti-mycobacterial therapy are often required for adequate suppression or eradication 2.
- Treatment is lengthy and varies by species, and therefore a challenge 4.
- The decision to start treatment for NTM lung disease is not easy and requires careful individualized analysis of risks and benefits 4.
- Treatment for NTM diseases usually involves the use of macrolides and injectable aminoglycosides 5.
- Although well-established international guidelines are available, treatment of NTM disease is mostly empirical and not entirely successful 5.
- The treatment duration is much longer for NTM diseases, compared to TB, and resection surgery of affected organ(s) is part of treatment for patients with NTM diseases that do not respond to the antibiotics treatment 5.
Epidemiology of Non-Tuberculous Mycobacterial (NTM) Tuberculosis
- The incidence and prevalence of NTM lung disease are increasing worldwide and rapidly becoming a major public health problem 4.
- NTM disease is primarily associated with bronchiectasis, this condition is rarely a predisposing factor for TB 5.
- In Human Immunodeficiency Virus (HIV)-infected individuals, NTM disease presents as disseminated, extrapulmonary form rather than as a miliary, pulmonary disease, which is seen in Mtb infection 5.
- Nontuberculous mycobacteria (NTM) are ubiquitous in the environment and 193 species of NTM have been discovered thus far 6.