Nontuberculous Mycobacteria: An update

Nontuberculous mycobacteria (NTM) are environmental pathogens increasingly recognized as significant causes of pulmonary and extrapulmonary infections worldwide. This review provides a detailed overview of NTM, emphasizing their rising prevalence, evolving diagnostic frameworks, and complex treatment paradigms. The most commonly implicated species in human disease include Mycobacterium avium complex (MAC), M. abscessus, and M. kansasii. These organisms cause a spectrum of diseases, most notably NTM pulmonary disease (NTM-PD), especially in individuals with preexisting lung conditions, structural abnormalities, or immunocompromised states. The diagnosis of NTM-PD is often challenging due to clinical overlap with tuberculosis and other chronic respiratory diseases. The 2020 ATS/IDSA guidelines recommend a triad of clinical symptoms, radiographic findings (e.g., bronchiectasis or cavitary lesions), and microbiological confirmation (≥2 positive sputum cultures or one bronchoscopic lavage) for diagnosis. Accurate species identification and susceptibility testing are essential due to interspecies variation in drug responsiveness. Management of NTM-PD requires a multidisciplinary approach. Treatment regimens are guided by species type and drug susceptibility. Macrolide-based multidrug therapy is the cornerstone for MAC, while M. abscessus often requires prolonged intravenous therapy using amikacin, tigecycline, or imipenem, followed by oral agents. Novel therapies such as Omadacycline and Amikacin Liposome Inhalation Suspension (ALIS) offer promise for refractory cases. Non-pharmacological strategies, including airway clearance and nutritional support, are particularly important in bronchiectasis-associated disease. Management of NTM-PD requires a multidisciplinary approach. Treatment regimens are guided by species type and drug susceptibility. Macrolide-based multidrug therapy is the cornerstone for MAC, while M. abscessus often requires prolonged intravenous therapy using amikacin, tigecycline, or imipenem, followed by oral agents. The review also addresses briefly extrapulmonary manifestations of NTM infections, which may involve skin, lymph nodes, bone, and disseminated disease, especially in HIV-positive or immunosuppressed patients. Diagnostic vigilance is essential, as radiologic and microbiologic findings may be subtle or misleading. Coinfections with fungi or tuberculosis, and increasing reports of NTM following cosmetic or surgical procedures, further complicate clinical management. Given high relapse rates and complex drug regimens, long-term monitoring and individualized treatment plans are crucial. Future directions emphasize genotypic resistance testing, improved diagnostic criteria, and greater awareness among clinicians. As NTM incidence continues to rise worldwide, particularly in TB-endemic regions, timely diagnosis, tailored therapy, and expert consultation are vital for optimal outcomes. Clinicians must remain vigilant to address this growing public health concern effectively.