title: Evaluation of four colourimetric susceptibility tests for the rapid detection of multidrug-resistant Mycobacterium tuberculosis isolates.
abstract: The purpose of this study is to evaluate four rapid colourimetric methods, including the resazurin microtitre assay (REMA), malachite green decolourisation assay (MGDA), microplate nitrate reductase assay (MNRA) and crystal violet decolourisation assay (CVDA), for the rapid detection of multidrug-resistant (MDR) tuberculosis. Fifty Mycobacterium tuberculosis isolates were used in this study. Eighteen isolates were MDR, two isolates were only resistant to isoniazid (INH) and the remaining isolates were susceptible to both INH and rifampicin (RIF). INH and RIF were tested in 0.25 µg/mL and 0.5 µg/mL, respectively. The agar proportion method was used as a reference method. MNRA and REMA were performed with some modifications. MGDA and CVDA were performed as defined in the literature. The agreements of the MNRA for INH and RIF were 96% and 94%, respectively, while the agreement of the other assays for INH and RIF were 98%. In this study, while the specificities of the REMA, MGDA and CVDA were 100%, the specificity of the MNRA was lower than the others (93.3% for INH and 90.9% for RIF). In addition, while the sensitivity of the MNRA was 100%, the sensitivities of the others were lower than that of the MNRA (from 94.1-95%). The results were reported on the seventh-10th day of the incubation. All methods are reliable, easy to perform, inexpensive and easy to evaluate and do not require special equipment.
authors.affiliation: Department of Medical Microbiology, Medical School Samsun, Ondokuz Mayis University, Samsun, TR.
authors.forename: Ahmet Yilmaz
authors.initials: AY
authors.lastname: Coban
authors.affiliation: Department of Medical Microbiology, Medical School Samsun, Ondokuz Mayis University, Samsun, TR.
authors.forename: Ahmet Ugur
authors.initials: AU
authors.lastname: Akbal
authors.affiliation: Department of Medical Microbiology, Istanbul Medical School, Istanbul University, Istanbul, TR.
authors.forename: Meltem
authors.initials: M
authors.lastname: Uzun
authors.affiliation: Department of Medical Microbiology, Medical School Samsun, Ondokuz Mayis University, Samsun, TR.
authors.forename: Belma
authors.initials: B
authors.lastname: Durupinar
mesh_terms: D000995:Antitubercular Agents / Q000494:pharmacology*; D004396:Coloring Agents; D024901:Drug Resistance, Multiple, Bacterial / Q000187:drug effects*; D006801:Humans; D007202:Indicators and Reagents; D008826:Microbial Sensitivity Tests / Q000379:methods*; D009169:Mycobacterium tuberculosis / Q000187:drug effects*; D012680:Sensitivity and Specificity
chemical_list: D000995:Antitubercular Agents; D004396:Coloring Agents; D007202:Indicators and Reagents