Journal Article

Comparative evaluation of the nitrate reduction assay, the MTT test, and the resazurin microtitre assay for drug susceptibility testing of clinical isolates of <i>Mycobacterium tuberculosis</i>

Ernesto Montoro, Dihadenys Lemus, Miguel Echemendia, Anandi Martin, Françoise Portaels and Juan Carlos Palomino

in Journal of Antimicrobial Chemotherapy

Published on behalf of British Society for Antimicrobial Chemotherapy

Volume 55, issue 4, pages 500-505
Published in print April 2005 | ISSN: 0305-7453
Published online April 2005 | e-ISSN: 1460-2091 | DOI: http://dx.doi.org/10.1093/jac/dki023
Comparative evaluation of the nitrate reduction assay, the MTT test, and the resazurin microtitre assay for drug susceptibility testing of clinical isolates of Mycobacterium tuberculosis

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Objectives: To evaluate the performance of three rapid low-cost methods for the detection of resistance to first-line drugs in Mycobacterium tuberculosis.

Methods: One hundred M. tuberculosis clinical isolates were tested by the nitrate reductase assay (NRA), the MTT test and the resazurin microtitre assay (REMA), and the results compared with those obtained with the gold standard proportion method (PM) on Löwenstein Jensen medium.

Results: The results using the three methods showed a good sensitivity and specificity between 94% and 100% for the detection of rifampicin and isoniazid resistance. Specificity for ethambutol and streptomycin using MTT and resazurin was low (58–89%). In contrast, NRA showed a good agreement for all first-line drugs tested.

Conclusions: This study shows a high level of agreement of these three low-cost methods compared with the PM for rapid detection of rifampicin and isoniazid resistance. However, more standardization is needed for ethambutol and streptomycin using the MTT test and resazurin microtitre assay. The nitrate reductase assay might represent an inexpensive procedure for rapid detection of resistance to first-line drugs in low-resource countries.

Keywords: antibiotic resistance; colorimetric; rapid methods

Journal Article.  3383 words.  Illustrated.

Subjects: Medical Oncology ; Critical Care

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