Utility of gas chromatography for the identification of mycobacterial species

The human immunodeficiency virus (HIV) epidemic has altered the epidemiolog ical profile of tuberculosis in both industrialized and developing countrie s. Serious diseases caused by mycobacteria other than Mycobacterium tubercu losis, mostly belonging to the M, avium-intracellulare complex (MAC), have become very common in association with severe immunosuppresion. The increas e in mycobacterial disease complexity has stimulated the development of mor e rapid and efficient methods for diagnosis. In the present study, we inves tigated and assessed the suitability of a gas-liquid chromatography techniq ue for diagnosis of clinically important mycobacteria in Argentina. An iden tification scheme was developed from the results obtained in a previous stu dy where we characterized the cellular fatty acids and the mycolic acid cle avage products from most frequent species in Argentina. Or 183 isolates tes ted, 69% were correctly identified to species level and 5% were incorrectly classified. If we only take into account the isolates that could be identi fied, 93% were correctly identified. Although all of the isolates of M. tub erculosis were correctly identified, four isolates of MAC were incorrectly matched by M. tuberculosis. Gas chromatography provides a rapid technique o f highly predictive value for mycobacteria identification; it could be used in reference laboratories as a rapid presumptive identification until the biochemical tests are completed.