A new rapid colourimetric method for testing
Mycobacterium tuberculosis susceptibility to isoniazid and
rifampicin: a crystal violet decolourisation assay |
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Authors: | Ahmet Yilmaz Coban |
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Institution: | Department of Medical Microbiology, Medical School, Ondokuz Mayis University, Samsun,Turkey |
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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 -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. |
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Keywords: | Mycobacterium tuberculosis multidrug resistance susceptibility testing isoniazid rifampicin crystal violet decolourisation assay |
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