Mutation position and type of substitution in the β-subunit of the RNA polymerase influence in-vitro activity of rifamycins in rifampicin-resistant Mycobacterium tuberculosis

Quantitative susceptibility testing for rifampicin, rifabutin and rifapentine of 36 Mycobacterium tuberculosis isolates with known sequences for the gene encoding for the RNA polymerase β-subunit (rpoB)revealed that both mutation position and type of amino acid substitution influence the in-vitro activity of rifamycins in rifampicin-resistant strains.