Direct Detection of Rifampin-Resistant Mycobacterium Tuberculosis by Polymerase Chain Reaction and Line Probe Assay in Sputums

Lee, Mi Ae

Abstract

BACKGROUND: Recently, the control of tuberculosis may be threatened by widespread emergence of multidrug-resistant tuberculosis. Rifampin resistance is considered as a useful marker of multidrug-resistant tuberculosis and is developed by missense mutations in region of the rpoB gene encoding the beta-subunit of RNA polymerase. This study aimed to evaluate the line probe assay for direct detection of rifampin-resistant Mycobacterium tuberculosis in clinical samples.
METHODS
Twenty-seven smear-positive and 13 smear-negative clinical samples, 13 M. tuberculosis strains and 2 nontuberculous mycobacteria strains were analyzed with line probe assay (Innogenetics, Belgium) and results were compared with conventional susceptibility test. I also reviewed conventional antimicrobial susceptibility testing patterns of 128 M. tuberculosis isolates from January 1996 to March 1997.
RESULTS
All (100%) of total 30 patients who had rifampin-resistant strains revealed 3 or more drug resistances, but 5 (5%) out of 88 patients who had rifampin-sensitive strains revealed 2 or more drug resistances. By the line probe assay, 3 out of 13 smear-negative samples, 6 out of 27 smear-positive samples and 6 out of 13 M. tuberculosis strains were rifampin-resistant. Overall concordance of the line probe assay with conventional susceptibility test was 100%. Most common mutation site of rpoB gene was codon 531 (53.3%) followed by codon 526 (40%) and codon 516 (6.7%).
CONCLUSIONS
These suggest that rifampin resistance will be a useful marker of multidrug- resistant tuberculosis and line probe assay will be a rapid and direct diagnostic tool for the detection of rifampin-resistant M. tuberculosis in clinical samples, especially AFB smear-negative samples.