Pulmonary infections associated with non-tuberculous mycobacteria in immunocompetent patients

A decline in the prevalence of tuberculosis in the developed world over the past several years has been accompanied by an increase in the rate of mycobacterial disease caused by non-tuberculous mycobacteria. However, it is still unclear whether there is a real increase in prevalence or whether non-tuberculous mycobacterial disease is being recognised more frequently by clinicians in a variety of clinical settings, thus enhancing the competence of microbiologists to detect the more unusual and fastidious mycobacteria. The introduction of liquid media for isolation of mycobacteria coupled with more accurate methods for identification have allowed several new species associated with human disease to be recognised. Despite this progress, several issues related to non-tuberculous mycobacterial infections need to be addressed, including the timely and reliable identification of isolates, standardisation and clinical evaluation of susceptibility testing, and capability to distinguish disease-causing isolates from contaminant or saprophytic species. Treatment regimens for non-tuberculous mycobacterial disease are still largely undefined and outcome remains disappointing despite substantial upgrading in laboratory diagnosis and the availability of new antimicrobials. Treatment success is impaired by the long duration of regimens, side-effects, and drug interactions, which prevent patients from full compliance. We discuss the epidemiological features, clinical syndromes, and developments in the investigation, prevention, and treatment of pulmonary non-tuberculous mycobacterial infections.