Insertion sequence fingerprinting and transpositional activity in mycobacteria.

The insertion sequence IS6110 has been shown to be present only in members of the Mycobacterium tuberculosis complex. In this report, probes derived from a copy of IS6110 from M. tuberculosis, namely IS986, have been employed to fingerprint M. tuberculosis, BCG and M. bovis. BCG vaccine strains Brazil, Japan and Russia are shown to possess two copies of the insertion sequence at the sites BCG1 and BCG2 respectively, while the rest of the BCG substrains possess only one copy which is present at BCG1. M. tuberculosis isolates from Tanzania were seen to vary widely in their restriction fragment length polymorphism (RFLP) patterns, but groupings of these isolates were achieved employing the MolMatch analysis program. Some rare but widely distributed isolates of M. tuberculosis were analyzed and their relation to BCG assessed by employing Southern blots of restriction digests and the polymerase chain reaction. These strains were initially thought to have IS6110 at the BCG2 position, but PCR analysis indicated it might be at the BCG1 position. IS6110 typing of M. bovis strains from animal and human sources indicated most of these strains possessed only single copy of IS6110 which was mainly located at BCG2 although a few strains had IS6110 located at the BCG2 position (but on rare occasions, at a position between BCG1 BCG2), while the isolates with multicopies had two or three copies. Strains from human origins were also observed to be more likely to harbor multiple copies of IS6110 than those from an animal origin. Experimental demonstration of transposition of IS986 was also achieved, giving a range of structures from cointegrates, to genuine transposition and other structures not defined by conventional transposition models. These results have been analyzed and their significance fully discussed in the ensuing chapters