Novel diagnostic approaches to the recovery of nontuberculous mycobacteria from clinical samples

The genus Mycobacterium consists of more than 200 species, many of which play pivotal roles in the health and well-being of humans and other forms of life. Aside from the innately pathogenic Mycobacterium tuberculosis complex (MTBC) and M. leprae, an array of nontuberculous mycobacteria (NTM) exists. NTM pulmonary infections are increasingly common and problematic for immunocompromised individuals as well as those with a chronic pre-existing lung condition such as cystic fibrosis (CF) and bronchiectasis. A new selective agar was developed for the isolation of rapidly growing NTM directly from patient sputum. The different clinical approaches used for CF patient samples were utilised to compare the novel medium against the current media used. The novel medium incubated at 30°C was found to recover more NTM than at 37°C, including significantly more Mycobacterium abscessus complex (MABSC) compared to routine mycobacterial culture. The requirement of decontamination was also challenged by investigating the presence of NTM (namely MABSC) in non-TB patients. The new medium was found to be highly selective for the isolation of NTM when compared to the impact of several decontamination methods. Most notably, MABSC recovery and colony counts were negatively impacted by treatments containing NaOH, compared to the direct inoculation onto the novel medium. The novel medium is not only used in clinical settings, as recent studies have also shown that this highly selective medium is a valuable method for testing environmental water samples simplifying the recovery of NTM and the subsequent monitoring of the environmental samples.