Clinical significance of mycobacterium other than tuberculosis isolated from respiratory specimens at a university hospital

Abstract

Background: Mycobacteria other than tuberculosis (MOTT) are ubiquitous and have been recognized to cause pulmonary disease. Because of newer laboratory diagnostic techniques, it has become more frequent to identify MOTT from pulmonary specimens. The objective of this study was to determine the spectrum of MOTT in pulmonary specimens in hospitalized patients and determine their clinical significance.

Methods: A retrospective study of all cases of positive pulmonary specimens cultured for MOTT in patients admitted to University of Louisville Hospital from January 1989 to December 1992 was performed. A determination of whether or not the MOTT caused pulmonary disease was made, using the criteria required by the American Thoracic Society.

Results: There were 221 positive pulmonary specimen cultures for mycobacteria, of which 164 were MOTT and 57 were M tuberculosis. Of the MOTT isolates, 82 (50%) were M gordonae; 44 (27%) M avium intracellulare; 18 (11%) M chelonae; 12 (7%) M fortuitum; 2 (1%) M kansasii; 2 (1%); M scrofulaceum; 2 (1%) M xenopi; and 2 (1%) M terrae. From all the MOTT cases, only one met the criteria for MOTT pulmonary disease. The rest were found to be non-pathogens, either colonizers or contaminants.

Conclusion: Newer laboratory diagnostic techniques are improving isolation and identification of MOTT. Even though reports of positive pulmonary specimens for MOTT are becoming more numerous, MOTT was found to be a rare pulmonary pathogen in our hospital, when strict criteria were used.