INSERTION-SEQUENCE TYPING OF MYCOBACTERIUM-TUBERCULOSIS - CHARACTERIZATION OF A WIDESPREAD SUBTYPE WITH A SINGLE-COPY OF IS6110

DNA fingerprinting with the insertion sequence IS6110 (also known as I S986) has become established as a major tool for investigating the spr ead of tuberculosis, Most strains of Mycobacterium tuberculosis have m ultiple copies of IS6110, but a small minority carry a single copy onl y, We have examined selected strains from Malaysia, Tanzania and Oman, in comparison with M. bovis isolates and BCG strains carrying one or two copies of IS6110, The insertion sequence appears to be present in the same position in all these strains, which suggests that in these o rganisms the element is defective in transposition and that the loss o f transposability may have occurred at an early stage in the evolution of the M. tuberculosis complex.