[Significance of RFLP analysis for community-based control against tuberculosis].

Purpose: The purpose of this study is to obtain an index for measures against tuberculosis by elucidation of the source/route of infections and prevention of secondary infection by RFLP analysis in Okayama.
Methods: A total of 474 strains isolated in Okayama prefecture from April 2000 to March 2004 were subjected to RFLP analysis. Analysis was only performed for mycobacterial strains from patients whose ages and places of residence were known. The prevalent situation of tuberculosis was analyzed by the distribution of IS6110 copy numbers, and the prevalent strains were examined by cluster analysis of RFLP patterns. To speculate regarding the mode of infections, annual change of RFLP patterns and differences in RFLP patterns with the age group and area were examined. A database was made with the results of RFLP analysis and information about bacterial strains from a public health center and monitored in order to discover latent links to outbreak or sporadic cases.
Results: The RFLP patterns for the 474 strains reflected past tuberculosis in highly prevalent times. Among 37 sets of clusters which showed the same pattern (110 strains), relationships were recognized between the patients in 20%. Most of the patients were younger than 60 years of age. By classification according to the similarity of RFLP patterns, three prevalent strain groups were recognized, to which about 40% of all strains belonged. Judging from the RFLP pattern distribution, there was no obvious annual change. The age groups of the patients and the areas where they lived did not influence the RFLP patterns of mycobacteria. Therefore, it was concluded that infection of the various age groups occurred with mycobacteria from reactivated older generation. Accordingly, prevention of tuberculosis reactivation in the aged can be considered the most important measure against tuberculosis.
Conclusions: We obtained basic data on the prevalence for tuberculosis and the prevalent strains in Okayama by RFLP analysis. Together with conventional epidemiological investigation the resulting database allows scientific analysis of cases, although latent links to outbreak or sporadic cases were not revealed in this study. Further analyses with the database should contribute to measures against tuberculosis.