Molecular characterization of Mycobacterium tuberculosis isolates from Łódź, Poland: analysis by IS6110 restriction fragment length polymorphism and double-repetitive-element PCR

Abstract

Objectives: The aim of the present study was to characterize Mycobacterium tuberculosis strains isolated in the area of Łódź, Poland, from 1996 to 2000.

Methods: Two hundred sixty three isolates from 250 patients with tuberculosis were analysed by IS6110 restriction fragment length polymorphism (RFLP) and the double-repetitive-element PCR (DRE-PCR) method when indicated.

Results: The isolates were found to show a great heterogeneity and only 52 strains (20.8%) occurred in 20 clusters of 2-5 identical clones. Despite this diversity of IS6110 RFLP patterns, a computer analysis of similarities revealed a high level of relatedness (at least 90%) among 38.4% of different patterns. Most of the patients with clustered strains showed no apparent epidemiologic links with other patients whose strains had the same pattern. Utilisation of the DRE-PCR analysis as an additional typing test allowed to differentiate M. tuberculosis strains with a discriminating capacity similar to that of the IS6110 RFLP. Also, DRE-PCR differentiated nine strains that were indistinguishable by the RFLP analysis.

Conclusions: Both methods used for the molecular characterization of M. tuberculosis clinical isolates showed similar discriminating ability. DRE-PCR analysis proved a simple, rapid and cost-effective adjunct to the IS6110 RFLP reference method. It could be applied as a screening test, thus, reducing the number of isolates that need further subtyping with the IS6110 RFLP to those initially clustered.