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Updated: Aug 30, 2026
System for Efficacy and Cytotoxicity Screening of Inhibitors Targeting Intracellular Mycobacterium tuberculosis
Published on: April 5, 2017
Rapid colorimetric method for testing susceptibility of Mycobacterium tuberculosis to isoniazid and rifampin in
1Department of Microbiology and Immunology, The Gade Institute and Haukeland University Hospital, University of Bergen, N-5021 Bergen, Norway.
Abstract:
We have developed a rapid colorimetric method for testing the susceptibility of M. tuberculosis to isoniazid (INH) and rifampin (RIF) based on incorporation of nitrate in broth cultures containing growth supplements. The performance of this colorimetric nitrate reductase-based antibiotic susceptibility (CONRAS) test was compared with that of the radiometric BACTEC 460TB system in determining the susceptibilities of 74 M. tuberculosis strains to INH and RIF. By using the BACTEC 460TB system as the "gold standard," the sensitivity (i.e., the ability to detect true drug resistance) and specificity (i.e., the ability to detect true drug susceptibility) of the CONRAS test were 100 and 95% for INH and 94 and 100% for RIF, respectively. The repeatability of the CONRAS test was excellent (for INH, kappa = 1 and P < 0.001; for RIF, kappa = 0.88 and P < 0.001). For the majority of strains, results were obtained within 5 days. The CONRAS test is rapid, accurate, and inexpensive and is an adequate alternative, particularly for resource-poor countries.
