[Atypical mycobacteria and pulmonary involvement in infectious diseases]

Nontuberculous mycobacteria (NTM) are increasingly associated with infectious pulmonary disease. NTM are ubiquitous environmental pathogens with high isolation rates worldwide. The greater frequency of NTM associated with pulmonary diseases is probably due to a combination of increased exposure, improved diagnostic methods and an increase in the prevalence of risk factors predisposing individuals to infection. Difficulty may arise in determining whether an isolate from a respiratory sample is in fact a contaminant or a pathogenic organism. The ATS/IDSA guidelines highlight the importance of following microbiological and clinical criteria in making a diagnosis of NTM lung infection. These criteria may not be useful for all NTM and species-level identification is strongly recommended. Mycobacteria identification by conventional methods has been the standard in most clinical microbiology laboratories. However, conventional testing alone does not allow identification of many NTM. Newer, rapid molecular methods such as commercially available nucleic acid probes, genomic amplification and DNA sequence analysis should be used. Communication between the clinician and the laboratorian is essential to decide whether an isolate could be sent to a reference laboratory to determine the best method for species identification. Although the CLSI has recently published an approved standard for NTM susceptibility testing, there is ongoing debate about the role of in vitro susceptibility for managing patients with NTM disease. The goal of this review is to describe the mycobacteria involved in lung disease, the factors that predispose to this infection, its diagnosis with alternative procedures and the correlation between in vitro and in vivo treatment response.