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Memórias do Instituto Oswaldo Cruz
Fundação Oswaldo Cruz, Fiocruz
ISSN: 1678-8060
EISSN: 1678-8060
Vol. 109, No. 2, 2014, pp. 246-249
Bioline Code: oc14033
Full paper language: English
Document type: Research Article
Document available free of charge

Memórias do Instituto Oswaldo Cruz, Vol. 109, No. 2, 2014, pp. 246-249

 en A new rapid colourimetric method for testing Mycobacterium tuberculosis check for this species in other resources susceptibility to isoniazid and rifampicin: a crystal violet decolourisation assay
Coban, Ahmet Yilmaz

Abstract

The aim of this study was to investigate the performance of a new and accurate method for the detection of isoniazid (INH) and rifampicin (RIF) resistance among Mycobacterium tuberculosis check for this species in other resources isolates using a crystal violet decolourisation assay (CVDA). Fifty-five M. tuberculosis isolates obtained from culture stocks stored at -80oC were tested. After bacterial inoculation, the samples were incubated at 37oC for seven days and 100 μL of CV (25 mg/L stock solution) was then added to the control and sample tubes. The tubes were incubated for an additional 24-48 h. CV (blue/purple) was decolourised in the presence of bacterial growth; thus, if CV lost its colour in a sample containing a drug, the tested isolate was reported as resistant. The sensitivity, specificity, positive predictive value, negative predictive value and agreement for INH were 92.5%, 96.4%, 96.1%, 93.1% and 94.5%, respectively, and 88.8%, 100%, 100%, 94.8% and 96.3%, respectively, for RIF. The results were obtained within eight-nine days. This study shows that CVDA is an effective method to detect M. tuberculosis resistance to INH and RIF in developing countries. This method is rapid, simple and inexpensive. Nonetheless, further studies are necessary before routine laboratory implementation.

Keywords
Mycobacterium tuberculosis; multidrug resistance; susceptibility testing; isoniazid; rifampicin; crystal violet decolourisation assay

 
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