Non-Tuberculous Mycobacteria. An Emerging Threat?

Introduction And Objective: Non-tuberculous mycobacteria (NTM) isolates are becoming more common. The main objective of our study was to establish the number and diversity of NTM species in our region and their distribution according to the source sample, age and gender of the patients, and to analyse clinically significant isolates.

Methodology: Prospective study of all NTM isolated in Asturias from 2005 to 2012. Samples were processed following internationally accepted guidelines. Statistical analysis was based on Fisher's exact test for 2×2 contingency tables.

Results: A total of 3,284 mycobacteria were isolated: 1,499 Mycobacterium tuberculosis complex (MTB) and 1,785 NTM.During the study, NTM isolation rates increased while MTB isolation decreased. NTM were more frequent in men (P<.001). M.gordonae was the most frequently isolated species but did not cause disease in any case. NTM isolates from 212 patients were associated with clinically significant disease (17.1%). M.kansasii and M.avium were most commonly associated with disease. The number of M.kansasii isolates from men was statistically significant (P<.01).

Conclusions: In our study, NTM isolates increased by 35%, compared with a 21% decline in cases of MTB. Both isolation of NTM and clinically significant cases were more common in men. Only 17.1% of NTM isolates were associated with disease, most commonly M.avium complex and M.kansasii.