Identification of mycobacteria by mycolic acid pattern

Tuberculosis caused by Mycobacterium tuberculosis is a public health problem which has increased in importance during the last 12 years, due in part to the increasing number of cases caused by the association of acquired immunodeficiency syndrome (AIDS) and the appearance of multiple drug-resistant strains. Other mycobacteria which are often indistinguishable from tuberculosis have also increased.

Mycolic acid patterns were obtained from 53 clinical isolates of sputum, cerebrospinal fluid, bronchial washing, corneal ulcer, and bone marrow, as well as from 11 acid-fast stain smear-positive clinical specimens. Standardized mycolic acid extraction method was used to ensure the maximal extraction of mycolic acid derivatives to enhance the sensitivity of the method. A chromatographic column different from what others have employed and a different gradient elution from those reported in the literature were used, making a correlation between retention times for the chromatographic peaks obtained in this study and those previously reported for mycolic acid patterns from a strain of Mycobacterium avium necessary. Then, a comparison of retention times of mycolic acid pattern obtained in this study and those previously reported in the literature was carried out. Strains were identified as Mycobacterium tuberculosis complex, Mycobacterium avium complex, Mycobacterium fortuitum, Mycobacterium chelonae and Mycobacterium kansasii in less than 24 hours.

In direct analysis of acid-fast stain smearpositive from 1+ to 4+ specimens, mycolic acid patterns were identified as Mycobacterium tuberculosis complex, Mycobacterium avium complex, Mycobacterium chelonae, and Mycobacterium kansasii, with a strong signal even in light 1+ positive samples.

The results showed that identification of mycobacteria through mycolic acid pattern is a rapid, sensitive, and very useful method for identification of mycobacteria in the early diagnosis of the mycobacteriosis.