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Journal of Clinical Microbiology, 03 1995, 556-561, Vol 33, No. 3
AC Whelen, TA Felmlee, JM Hunt, DL Williams, GD Roberts, L Stockman and DH Persing
Recent analysis of the gene encoding the beta subunit of Mycobacterium
tuberculosis RNA polymerase (rpoB) has demonstrated a small region that
harbors the mutations most frequently associated with rifampin resistance.
Earlier reports have described a high degree of sequence conservation of
rpoB among mycobacteria other than M. tuberculosis and other GC-rich
bacteria that can lead to false-positive amplification when applied
directly to clinical specimens. We developed reagents for PCR amplification
that are based on signature nucleotides discovered by comparative sequence
analysis of the rpoB genes of organisms phylogenetically related to M.
tuberculosis. The specificities of the reagents were challenged with 20
isolates of multiple-drug-resistant M. tuberculosis and more than 20
species of mycobacteria other than M. tuberculosis and other GC-rich
organisms. A single-tube heminested PCR protocol was devised to obtain
sensitivity equal to those of an IS6110- based PCR assay and culture in
spiked sputum experiments. The assay correctly identified 21 of 24 (87.5%)
culture-positive specimens, 13 of which were acid-fast smear-negative, in a
panel of 51 clinical specimens. Three specimens that were false-positive
initially were negative upon repeat testing when the assay was modified to
eliminate the potential for aerosol carryover of the first-round
amplification product during the open-tube addition of the second set of
reaction reagents. This assay is the most sensitive and specific test to
date for the direct detection of M. tuberculosis rpoB in clinical
specimens. This rapid PCR-based assay can be used for the simultaneous
identification of M. tuberculosis and its rifampin susceptibility genotype.
Copyright © 1995 by the American Society for Microbiology. All rights reserved.
Direct genotypic detection of Mycobacterium tuberculosis rifampin resistance in clinical specimens by using single-tube heminested PCR
Division of Clinical Microbiology, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA.
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