In vitro activity of rifabutin and rifampin against clinical isolates of Mycobacterium tuberculosis in Taiwan.
OBJECTIVE
To determine the in vitro activity of rifabutin against Mycobacterium tuberculosis (MTB) and the cross-resistance rate between rifampin and rifabutin.


METHODS
A total of 56 clinical isolates of MTB, including 23 multidrug-resistant (MDR) isolates and 33 susceptible isolates, were tested for susceptibility to rifampin and rifabutin using the absolute concentration method. The concentrations of drugs tested were 2.5 and 5 mg/mL for rifampin and 0.1, 0.5, 1, 2.5, 5, and 10 mg/mL for rifabutin.


RESULTS
All 33 MTB isolates that were susceptible to rifampin were also susceptible to rifabutin. None of the 23 MDR-MTB isolates were inhibited by rifabutin at a concentration of 0.1 mg/mL. Among these 23 MDR isolates, three were susceptible to rifabutin at concentrations > or = 0.5 mg/mL, six were susceptible to rifabutin at concentrations > or = 5 mg/mL, 18 were susceptible to rifabutin at concentrations > or = 10 mg/mL and five were not inhibited at any of the concentrations tested. The cross-resistance rate between rifampin and rifabutin was 87%.


CONCLUSIONS
Our results indicate that the in vitro activity of rifabutin against drug-susceptible MTB isolates is greater than that of rifampin. For MDR-MTB isolates, the cross-resistance is high between rifampin and rifabutin.
Chien
H P
HP
Taiwan Provincial Chronic Disease Control Bureau, Taipei, Taiwan.
Yu
M C
MC
Ong
T F
TF
Lin
T P
TP
Luh
K T
KT
D000904:Antibiotics, Antitubercular / Q000494:pharmacology*; D004352:Drug Resistance, Microbial; D006801:Humans; D008826:Microbial Sensitivity Tests; D009169:Mycobacterium tuberculosis / Q000187:drug effects*; D017828:Rifabutin / Q000494:pharmacology*; D012293:Rifampin / Q000494:pharmacology*
D000904:Antibiotics, Antitubercular; D017828:Rifabutin; D012293:Rifampin