A new rapid colourimetric method for testing Mycobacterium tuberculosis susceptibility to isoniazid and rifampicin: a crystal violet decolourisation assay

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Coban A. Y.

MEMORIAS DO INSTITUTO OSWALDO CRUZ, vol.109, no.2, pp.246-249, 2014 (SCI-Expanded) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 109 Issue: 2
  • Publication Date: 2014
  • Doi Number: 10.1590/0074-0276140297
  • Journal Name: MEMORIAS DO INSTITUTO OSWALDO CRUZ
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.246-249
  • Keywords: Mycobacterium tuberculosis, multidrug resistance, susceptibility testing, isoniazid, rifampicin, crystal violet decolourisation assay, NITRATE REDUCTASE ASSAY, RESAZURIN MICROTITER ASSAY, RESISTANT TUBERCULOSIS, MULTIDRUG-RESISTANT, COLORIMETRIC METHOD, DRUG-RESISTANCE, MALACHITE GREEN, METAANALYSIS
  • Ondokuz Mayıs University Affiliated: No

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 isolates using a crystal violet decolourisation assay (CVDA). Fifty-five M. tuberculosis isolates obtained from culture stocks stored at -80 degrees C were tested. After bacterial inoculation, the samples were incubated at 37 degrees C for seven days and 100 mu L 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.