USE OF A PCR METHOD BASED ON IS6110 POLYMORPHISM FOR TYPING MYCOBACTERIUM-TUBERCULOSIS STRAINS FROM BACTEC CULTURES

Two PCR typing methods, based on polymorphism of the insertion sequenc e IS6110, were compared with Mycobacterium tuberculosis strains by usi ng a single primer complementary to the inverted repeats of IS6110. To tal M. tuberculosis DNA either was amplified directly (LS6110-PCR) or was amplified following digestion and ligation (IS6110-inverse-PCR). B oth PCR techniques showed a similar degree of discrimination. Because of its simplicity, IS6110-PCR was chosen to confirm that a single M. t uberculosis strain was responsible for an outbreak of tuberculosis in a secondary school. IS6110-PCR was used to study the degree of differe ntiation in 85 clinical M. tuberculosis isolates from BACTEC 12B broth cultures. Results were consistent with those of the standardized IS61 10 restriction fragment length polymorphism (RFLP) analysis method, sh elving identical PCR types for identical RFLPs, although the degree of discrimination was greater by RFLP analysis. The study concludes that due to its simplicity, IS6110-PCR is a good screening method when qui ck differentiation between M. tuberculosis strains is needed because B ACTEC cultures may be used directly.