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[Genetic analysis of Mycobacterium tuberculosis in Norway 1994-98]
Ulf R Dahle1, Per Sandven, Einar Heldal
1Divisjon for smittevern Nasjonalt folkehelseinstitutt Postboks 4404 Nydalen 0403 Oslo.
Background:
This study was undertaken to determine the genetic diversity in the population of Mycobacterium tuberculosis in Norway and to detect the degree of transmission between patients. The quality of the culturing work was ascertained by analysing the data for possible cross-contamination.
Material And Methods:
Genotypic relationships among 92% of all strains isolated in Norway in 1994-98 were assessed using IS6110-restriction fragment length polymorphism analysis. The strains had been isolated from 717 different patients. For isolates with less than five copies of IS6110 the directly repetitive element was also used.
Results:
20 isolates (2.8%) represented false positive samples. The isolates from 14.5% of the native Norwegian patients and 19.7% of the foreign patients were part of one of 35 clusters.
Interpretation:
The results indicate that the degree of recent transmission of tuberculosis in Norway was low and that transmission between immigrants and native Norwegians was uncommon. The majority of cases were due to reactivation of previous disease.