Overview of Non Tuberculosis Mycobacterial Lung Diseases

Abstract

Nontuberculosis mycobacteria (NTM) are ubiquitous in nature and opportunistically infect different animals, including humans. Currently, NTM is emerging as an important cause of pulmonary infection among both immunocompromised and immunocompetent persons worldwide. The clinical relevance of pulmonary NTM varies among species while showing geographical heterogeneity in distribution as well as pathogenicity. The outcome of the respiratory NTM disease is a consequence of a complex interplay between microbial factors and host susceptibility. Furthermore, HIV infection, cystic fibrosis, cancer, underlying chronic lung disease and history of tuberculosis (TB) may be associated as risk factors for active nontuberculosis pulmonary diseases (NTMPD). The diagnosis of NTMPD requires the presence of symptoms, radiographic evidences, microscopic observations and definitive laboratory diagnostics. Lung infections resulted from a clinically significant NTM species should be treated with appropriate antimicrobial regimen. M. leprae and M. lepraemurium are uncultivable and require the intracellular milieu for survival and propagation [4]. The obligatory causative agents of the genus Mycobacterium, responsible for TB are classified into Mycobacterium tuberculosis complex (MTC). It comprises M. tuberculosis, M.bovis, M. africanum, M. microti [5], M. canettii [6], M. caprae [7], M. pinnipedii [8], M. mungi [9], M. orygis [10] and M. suricattae [11] species. M. tuberculosis, M. africanum, M. canettii and M. orygis cause TB primarily in human [4, 10], whereas M. bovis [12], M. microti [13], M. caprae [7] M. pinnipedii [8], M. mungi [9] and M. suricattae [11] infect cattle, domestic animals, goats, seals, mongooses and meerkats, respectively, and animal tuberculosis can also be zoonotic [14, 15]. However, geographical variation of the MTC species distribution has been identified. As an example, M. africanum is a common cause of human pulmonary TB (39%) as much as M. tuberculosis (55%) in West Africa [16]. In Ghana, 3% of pulmonary TB cases are represented by M. bovis, while 20% are M. africanum and 73% are M. tuberculosis [17].Other medically important mycobacteria such as M. avium, M. intracellulare complex, M. kansasii, M. marinum, M. fortuitum, M. chelonae complex, M. abscessus and M. scrofulaceum are known as nontuberculosis mycobacteria (NTM) species or atypical mycobacteria or mycobacteria other than tuberculosis (MOTT). They are responsible for diseases including lymphadenitis in children, chronic pulmonary diseases, skin and soft-tissue diseases and infections of the skeletal system [18]. NTM are ubiquitous in nature and are widely distributed in water, soil and animals. Among prevailing NTM species, only a few species have a clinical impact on humans as opportunistic pathogens [19]. M. avium complex (MAC), M. abscessus, M. kansasii, M. fortuitum, M. chelonae, M. szulgai, M. triviale and M. scrofulaceum are common NTM species that cause pulmonary diseases in human [20]. Additionally, M. riyadhense was recently proposed as a cau...

Nontuberculous Mycobacterial Pulmonary Disease in an Immunocompromised Patient

“…Also, sputum smear microscopy does not distinguish NTM from M. tuberculosis, as bacilli in both cases are acid-fast and morphologically similar in appearance. Adhikaram found that patients with NTM-PD have been erroneously diagnosed as having tuberculosis and multidrug-resistant tuberculosis in 4.5 to 15% and 18 to 20% cases, respectively [2]. Guidelines for detecting NTM-PD were established in 2007 by the American Thoracic Society and the Infectious Diseases Society of America [3].…”