Relationship between rifampin MICs for and rpoB mutations of Mycobacterium tuberculosis strains isolated in Japan

We analyzed the relationship between rifampin MICs and rpoB mutations of 40 clinical isolates of Mycobacterium tuberculosis. A point mutation in either codon 516, 526, or 531 was found in 13 strains requiring MICs of greater than or equal to 64 mu g/ml, while 21 strains requiring MICs of less than or equal to 1 mu g/ml showed no alteration in these codons. However 3 of these 21 strains contained a point mutation in either codon 515 or 533. Of the other six strains requiring MICs between 2 and 32 mu g/ml, three contained a point mutation in codon 516 or 526, while no alteration was detected in the other three. Our results indicate that the sequencing analysis of a 69-bp fragment in the rpoB gene is useful in predicting rifampin-resistant phenotypes.