Potential of Modern Methods of Rifampicin Susceptibility Testing in Detection of Heteroresistance of Mycobacterium tuberculosis Cultures

The objective : evaluation of potential of modern methods of rifampicin susceptibility testing in detection of heteroresistance of Mycobacterium tuberculosis cultures. Subjects and Methods . Mixtures of susceptible (H37Rv) and resistant (strain 5521 with XDR, with the rpoB Ser531Leu mutation) Mycobacterium tuberculosis strains were artificially created in proportions from 0% to 100%. Phenotypic methods (BACTEC MGIT 960, proportion method on Middlebrook 7H10 medium) and molecular genetic tests (TB-TEST, Amplitub-MLU-RV, AmpliTest MBT-Resist I) were used to test resistance to rifampicin. Results . Phenotypic methods revealed resistance to rifampicin with 1% resistant cells in the mixture. Molecular genetic methods showed variable detection thresholds: 5% (AmpliTest MBT-Resist I), 20% (TB-TEST), and 30% (Amplitub-MDR-RV). The authors demonstrate possibility of enhancing the sensitivity of domestic molecular genetic test systems by improving PCR data interpretation software, as well as the need to develop algorithms for tuberculosis diagnosing, taking into account limitations of the methods used.