Clinical significance of nontuberculous mycobacteria. A bacteriological survey of Swedish strains isolated between 1973 and 1981.

An account is rendered of mycobacteria other than Mycobacterium tuberculosis isolated from specimens sent for culture during 9 years. The possible etiological significance of these bacteria was estimated from clinical data and the degree of bacterial growth. Pulmonary infection was the most common nontuberculous manifestation in the adults. In about 50% of the patients with slowly growing mycobacteria in their respiratory tract, these bacteria were considered to be an etiological factor. This applied to the species of the M. avium-intracellulare (MAI) complex and M. xenopi. M. Kansasii, a common cause of lung disease in many other countries, was rarely isolated. The corresponding figure for the rapidly growing mycobacteria belonging to the M. fortuitum-chelonei complex was 15%. These patients were all severely debilitated by other diseases. Lymphadenitis was the most common nontuberculous infection in children, but occurred only in children not vaccinated with BCG. Bacteria of the MAI complex was the predominating cause. Lung infection caused by nontuberculous mycobacteria did not occur in children.