Mutations in rpoB gene in rifampin-resistant Mycobacterium tuberculosis isolates identified in the West-Bohemian region of the Czech Republic

Abstract number: P2045

Objectives: Laboratory of Mycobacteriology of the Department of Microbiology of the Faculty of Medicine in Plzen serves the whole West-Bohemian Region of the Czech Republic with ca 567 500 citizens and two centers specialized in tuberculosis treatment. In the last years, many new factories employed thousands foreign workers (usually from the Far East) have been opened in this region. Therefore, there is a permanent migration of the people in some cities. Interestingly, despite these social-geographical characteristics, the rifampin resistance in the Mycobacterium tuberculosis isolates seems to be low. The aim of this study was to determine the resistance mechanisms in the rifampin resistance isolates.

Methods: Since the February of 2004, the isolates of rifampin-resistant M. turberculosis have been stored. Resistance to rifampin was determined by a proportion method. A 305-bp region covering the 81-bp rifampin resistance determining region of the gene of b-subunit DNA-dependent RNA polymerase (rpoB) was amplified and sequenced.

Results: During the study period, 344 M. tuberculosis isolates were identified. Ten isolates were found to be resistant to rifampin (2.91%). Sequencing analysis of the rifampin resistance region revealed the single mutation in codon 531 (Ser – Leu) in all resistant isolates.

Conclusions: Our data indicate that the resistance to rifampin in the isolates collected in the industrial area of the Czech Republic is low. The resistance mechanism was identified as a mutation in codon 531 responsible for the cross-resistance to rifamycin derivatives (rifampin, rifapentine, rifabutin, and rifalazil). The typing based on insertion sequence IS6110 analysis and restriction fragment length polymorphism (RFLP) is ongoing.

This work was financed by a research project grant MSM0021620819.