Genetics of Mycobacterium tuberculosis and genotyping of drug resistance.

During the last decade, molecular genetics has been applied to the study of mycobacteria, of Mycobacterium tuberculosis in particular. The identification of plasmids and phages able to transfer DNA cloned from Escherichia coli to M. tuberculosis has allowed to draw important information on immunogenic proteins, drug resistance, virulence and mechanisms of mycolic acid biosynthesis. Insertion sequences have been isolated and used in diagnosis, strain typing and mutagenesis studies. The definition of functional promoters has enabled their use in the production of recombinant mycobacteria which can express foreign antigens. Furthermore, the identification of the molecular basis of drug resistance for major antituberculosis drugs has potentially allowed the applicability of methods of rapid determination of drug resistance in clinical laboratories.