Evaluation of method for secondary DNA typing of Mycobacterium tuberculosis with pTBN12 in epidemiologic study of tuberculosis

Secondary fingerprinting of Mycobacterium tuberculosis DNA with a probe containing the polymorphic GC-rich repetitive sequence present in pTBN12 has been found to have greater discriminating power than does fingerprinting with the insertion sequence IS6110 for strains carrying few copies of IS6110. To validate the use of pTBN12 fingerprinting in the molecular epidemiology of tuberculosis, M. tuberculosis isolates from 67 patients in five states in the United States and in Spain were fingerprinted with both IS6110 and pTBN12. Epidemiologic links among the 67 patients were evaluated by patient interview and/or review of medical records. The 67 isolates had 5 IS6110 fingerprint patterns with two to five copies of IS6110 and 18 pTBN12 patterns, of which 10 were shared by more than 1 isolate. Epidemiologic links are consistently found among patients whose isolates had identical pTBN12 patterns, whereas no links were found among patients whose isolates had unique pTBN12 patterns. This suggests that pTBN12 fingerprinting is a useful tool to identify epidemiologically linked tuberculosis patients whose isolates have identical IS6110 fingerprints containing fewer than six fragments.