Use of GenoType MTBDR plus assay for the detection of mycobacteria molecular rifampicin and isoniazid resistance

Summary Introduction. The main causes of drug-resistant TB is the use of improper treatment regimens, and incorrect diagnosis of patients. The rapid identification of drug resistance strain is an important challenge to ensure a rapid and adequate therapy of tuberculo- sis and to limit the dissemination of multidrug resistant strains. Isoniazid (INH) and ri- fampicin (RMP) are the main antituberculosis drugs, used in the treatment regimen rec- ommended by the WHO. The occurrence of resistance to these two basic medicines are considered to be one of several causes of treatment failure in patients with tuberculosis. Aim. The aim of this study was to compare the results of resistance to isoniazid and rifampicin obtained with the molecular and the phenotypic method. Material and methods. The MTBDR plus assay was performed on 60 strains Mycobac- terium tuberculosis complex, and the results were compared with the results of conven- tional drug susceptibility testing (Bactec MGIT 960). Results. In the analyzed group of 60 strains of mycobacterium tuberculosis, mutations in the rpoB gene were detected in 40 of 42 strains of M. tuberculosis phenotypically resist- ant to RMP (92.9%). In the group of 51 M. tuberculosis strains phenotypically resistant to INH, mutations in the katG gene and inhA gene were found in 46 (90.2%). The sensitivity, specificity and positive and negative predictive values of the MTBDR assay were respec- tively 82.9, 94.7, 97.1 and 72% for multidrug-resistant TB (MDR-TB). Conclusions. The GenoType MTBDR plus assay is a molecular test which detecting the most common mutations in strains resistant to RMP and INH. However the test does not detect all mutations associated with resistance to isoniazid and rifampicin, therefore, the results of molecular must be confirmed by phenotype.