Nontuberculous Mycobacteria Infections

Introduction to NTM

The European Respiratory Society recommends that mycobacteria causing lung infections be divided into Mycobacterium tuberculosis complex and nontuberculous mycobacteria (NTM), with the most common NTM pathogens being Mycobacterium avium complex (MAC), M. kansasii, M. xenopi among slowly growing species, and M. abscessus among rapidly growing species 1, 2, 3

The American Thoracic Society states that M. tuberculosis complex is the primary cause of tuberculosis and must be distinguished from NTM, as it requires different treatment approaches and has public health implications including human-to-human transmission 2, 3

The Infectious Diseases Society of America notes that MAC is the most common NTM causing pulmonary disease and now consists of 12 separate species 1, 2, 3, 4
The European Respiratory Society reports that the three most common MAC species causing pulmonary disease are M. avium, M. intracellulare, and M. chimaera 1, 2, 3, 4
MAC accounts for approximately 90% of disseminated NTM infections in HIV/AIDS patients with CD4 counts below 50 cells/µL 5, 6
The American College of Chest Physicians states that MAC typically affects middle-aged to elderly individuals, particularly those with underlying structural airway disease such as bronchiectasis or chronic obstructive pulmonary disease 1, 2, 7

The American Thoracic Society recommends that M. abscessus and its subspecies (abscessus, bolletii, and massiliense) be identified as the most common causative agents of pulmonary disease due to rapidly growing mycobacteria 1, 2, 3, 4

The Centers for Disease Control and Prevention note that in patients with advanced HIV infection (CD4 count <50 cells/µL), disseminated MAC disease is the predominant mycobacterial infection, with over 90% of disseminated NTM cases caused by MAC 5, 6
The Infectious Diseases Society of America reports that M. kansasii is the second most common NTM pathogen after MAC in HIV patients, though far less common than MAC 5, 6
The American College of Chest Physicians states that patients with underlying bronchiectasis or chronic obstructive pulmonary disease are at particularly high risk for NTM pulmonary disease 1, 2, 3, 7

The European Respiratory Society notes that only a small number of the over 190 known NTM species actually cause pulmonary disease in humans 1, 2, 9
The American Thoracic Society recommends that species-level identification is essential because treatment regimens, drug susceptibility patterns, and prognosis vary significantly between different mycobacterial species 1, 2, 3
The Infectious Diseases Society of America states that for M. abscessus, subspecies-level identification is required for optimal clinical and epidemiologic management 1, 2