Diagnosis of nontuberculous mycobacterial infections

Isolation of nontuberculous mycobacteria from a single sputum sample is not sufficient for diagnosis of respiratory infection, because this may simply reflect colonisation. Diagnosis in a symptomatic patient requires all of the following:

• at least two positive cultures from sputum, or at least one positive culture from bronchial lavage
• compatible radiological findings and evidence of progression
• exclusion of other diagnoses.

As nontuberculous mycobacteria are found in tap water, patients should avoid rinsing their mouths or drinking water immediately before sputum sample collection.