Mycolic acid analysis for clinical identification of Mycobacterium avium and related mycobacteria

We examined the mycolic acid composition of 133 strains belonging to MAIS complex (Mycobacterium avium-M. intracellulare-M. scrofulaceum) and MAIS intermediate strains and the related species M. asiaticum, M. malmoense, M. shimoidei, and M. simiae. The analysis revealed that about 10% of the strains identified as M. avium-M. intracellulare complex by conventional cultural and biochemical tests were in fact M. simiae strains according to their mycolate composition. Of 25 strains previously studied by the International Working Group on Mycobacterial Taxonomy, 2 (MAIS intermediate and M. asiaticum) presented patterns incompatible with the clusters to which they had been assigned. M. malmoense and both M. simiae serovars shared the same pattern with alpha-, alpha'-, and ketomycolates. We describe here the method used to identify the mycolic acid profiles in detail. We found it to be highly reproducible and convenient for use in mycobacterial reference laboratories.