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Journal of Clinical Microbiology, November 1999, p. 3524-3527, Vol. 37, No. 11
PHLS Mycobacterium Reference Unit,
Received 14 April 1999/Returned for modification 24 May
1999/Accepted 19 July 1999
New rapid phenotypic assays for the detection of rifampin
resistance in Mycobacterium tuberculosis have recently been
described, but most of these require liquid cultures, which reduces the
utility of many tests in terms of turnaround times. In the United
Kingdom, over 90% of rifampin-resistant isolates are also resistant to isoniazid, so rifampin resistance can be used as a sensitive marker for
multidrug-resistant tuberculosis. In this study, two new rapid phenotypic assays were compared to the standard resistance ratio method
on 91 clinical isolates of M. tuberculosis. One, the phage amplified biologically (PhaB) assay, has been described previously and
is based on the inability of susceptible isolates of M. tuberculosis to support the replication of bacteriophage D29 in
the presence of inhibitory doses of rifampin. The other employed
reverse transcription (RT)-PCR to demonstrate a reduction in inducible
dnaK mRNA levels in susceptible isolates treated with
rifampin. After incubation for 18 h with 4 µg of rifampin per
ml, the PhaB assay showed concordance with the resistance ratio method
for 46 of 46 (100%) susceptible and 31 of 31 (100%) resistant
isolates, while RT-PCR showed concordance for 46 of 48 (96%)
susceptible and 35 of 36 (97%) resistant isolates. We believe these
assays provide a reliable rapid means of susceptibility testing with a
total turnaround time of only 48 h, although the PhaB assay is
better in terms of its lower technical demand and cost and its
applicability to tuberculosis susceptibility testing in developing countries.
0095-1137/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Evaluation of Reverse Transcription-PCR and a
Bacteriophage-Based Assay for Rapid Phenotypic Detection of
Rifampin Resistance in Clinical Isolates of Mycobacterium
tuberculosis
*
Corresponding author. Mailing address: PHLS
Mycobacterium Reference Unit, Dulwich PHL and Department of
Microbiology, King's College School of Medicine and Dentistry, King's
College Hospital (Dulwich), East Dulwich Grove, London SE22 8QF, United
Kingdom. Phone: 0181-693-1312. Fax: 0171-346-6477. E-mail:
ijelt{at}aol.com.
Journal of Clinical Microbiology, November 1999, p. 3524-3527, Vol. 37, No. 11
0095-1137/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
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