RESTRICTION-FRAGMENT-LENGTH-POLYMORPHISM OF MYCOBACTERIUM-TUBERCULOSIS STRAINS ISOLATED FROM GREENLAND DURING 1992 - EVIDENCE OF TUBERCULOSIS TRANSMISSION BETWEEN GREENLAND AND DENMARK

In order to describe the transmission of tuberculosis (TB) at the clon al level in a defined geographic region during a certain period of tim e, all isolates of Mycobacterium tuberculosis collected during 1992 fr om Greenland were subjected to analyses of DNA restriction fragment le ngth polymorphism (RFLP). The RFLP patterns obtained by probing the ge nomic DNA with the repetitive insertion segment IS6110 revealed a high degree of similarity among the isolates, indicating a relatively high transmission rate and a close relationship between the individual M. tuberculosis clones. This was further confirmed by reprobing the South ern blots with two more-stable genetic markers, IS1081 and the DR sequ ence. The RFLP patterns were compared with those of 245 M. tuberculosi s strains collected from Denmark during the same period (representing 91% of all new, bacteriologically verified cases of TB in Denmark in 1 992). One of the three prevalent IS6110 defined clusters was traced to a group of immigrants from Greenland living in a small, defined geogr aphical region in Denmark and to a group of Danish citizens either wit h known contact with these immigrants or, in other cases, with a recor d of previous travel or working activities in Greenland. The study sho wed that the present technique is extremely helpful in monitoring the spread of TB and thereby also contributing to improved disease control .