[Molecular epidemiologic study of tuberculosis--a study on isolates of M. tuberculosis in southern half of Osaka...

Restriction fragment length polymorphism, RFLP or DNA fingerprinting technique provides a very useful tool for the study of epidemiology of tuberculosis transmission in human. We performed RFLP analysis with the IS6110 insertion sequence of the organisms isolated from culture-positive patients who visited our Hospital during the period from January to December 2001. Our Hospital covers patients living in southern half of Osaka Prefecture including a part of Osaka City, which is the highest TB prevalence area in Japan. The number of copies of IS6110 per isolate ranged from 1 to 21. Most isolates (67%) carried 10 to 15 copies. Of 410 available isolates during the year of 2001, 131 (32%) belonged to a cluster and 279 (68%) did not. The clusters comprised one matching isolate in minimum to 13 isolates in maximum and had a total of 49 distinct RFLP patterns. The average age of the clustered cases was 52.1 years and 64% cases belonged to patients with ages younger than 60 years. Above findings suggest that many cases of tuberculosis in southern part of Osaka Prefecture result from recent transmission. It remains to be elucidated, however, how and where these recent infections occurred in these clustered cases.