[Analysis of the antimycobacterial activities of rifabutin and the relationship between drug-resistance and rpoB mutations of Mycobacterium tuberculosis].
OBJECTIVE
To compare the antimycobacterial activities of rifampicin (RFP) and rifabutin (RBT), and to evaluate the correlation between RBT resistance and genetic alterations in the rpoB gene.


METHODS
The microplate-based alamar blue assay (MABA) method was performed to detect the antimycobacterial activities of RFP and RBT in 168 strains of Mycobacterium tuberculosis (M. tuberculosis). Meanwhile, we also analyzed the 81 bp core region of rpoB gene by DNA sequencing. The rate of gene mutations was analyzed by chi-square test.


RESULTS
RBT was sensitive for all of the 66 RFP-sensitive strains with no mutations in 81 bp core region of rpoB gene. But of the 102 RFP-resistant strains, 76 strains were also resistant to RBT. Cross resistance between RFP and RBT was 74.5% (76/102). Alterations at codons 516, 526, 531 in the rpoB gene correlated with resistance to both RFP and RBT. While point mutations at codons 511 and 533 possibly influenced the susceptibility to RFP but not to RBT. The mutation rate (92.1%, 70/76) of rpoB gene of RBT-resistant strains was significantly higher than that (23.9%, 22/92) of RBT-sensitive strains (χ(2) = 78.12, P < 0.05).


CONCLUSIONS
RBT was more active against M. tuberculosis as compared to RFP. The RFP-resistant strains with MIC ≤ 4 mg/L were still susceptible to RBT. Our results suggest that analysis of genetic alterations in the rpoB gene is useful for predicting RFP-resistance, and may have implications for evaluating RBT-resistance.
Department of Tuberculosis, Beijing Tuberculosis and Thoracic Tumor Research Institute, Beijing 101149, China.
Xi-qin
XQ
Han
Hai-rong
HR
Huang
Yan-jing
YJ
Li
Xia
X
Yu
Jing-tao
JT
Gao
Zhi-qiang
ZQ
Bi
Nai-hui
NH
Chu
Liang
L
Li
Yu
Y
Ma
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics*; D004252:DNA Mutational Analysis; D012321:DNA-Directed RNA Polymerases; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D017828:Rifabutin / Q000494:pharmacology*; D012293:Rifampin / Q000494:pharmacology*; D017422:Sequence Analysis, DNA
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; C505805:rpoB protein, Mycobacterium tuberculosis; D017828:Rifabutin; D012321:DNA-Directed RNA Polymerases; D012293:Rifampin