Rapid detection of multidrug-resistant
Mycobacterium tuberculosis using the malachite green
decolourisation assay |
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Authors: | Ahmet Yilmaz Coban Meltem Uzun |
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Institution: | 1.Department of Medical Microbiology, Medical School, Ondokuz Mayis University, Samsun, Turkey;2.Department of Medical Microbiology, Istanbul Medical School, Istanbul University, Istanbul, Turkey |
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Abstract: | Early detection of drug resistance in Mycobacterium tuberculosis
isolates allows for earlier and more effective treatment of patients. The aim of this
study was to investigate the performance of the malachite green decolourisation assay
(MGDA) in detecting isoniazid (INH) and rifampicin (RIF) resistance in M.
tuberculosis clinical isolates. Fifty M. tuberculosis
isolates, including 19 multidrug-resistant, eight INH-resistant and 23 INH and
RIF-susceptible samples, were tested. The sensitivity, specificity, positive
predictive value (PPV), negative predictive value (NPV) and agreement of the assay
for INH were 92.5%, 91.3%, 92.5%, 91.3% and 92%, respectively. Similarly, the
sensitivity, specificity, PPV, NPV and agreement of the assay for RIF were 94.7%,
100%, 100%, 96.8% and 98%, respectively. There was a major discrepancy in the tests
of two isolates, as they were sensitive to INH by the MGDA test, but resistant by the
reference method. There was a minor discrepancy in the tests of two additional
isolates, as they were sensitive to INH by the reference method, but resistant by the
MGDA test. The drug susceptibility test results were obtained within eight-nine days.
In conclusion, the MGDA test is a reliable and accurate method for the rapid
detection of INH and RIF resistance compared with the reference method and the MGDA
test additionally requires less time to obtain results. |
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Keywords: | Mycobacterium tuberculosis malachite green decolourisation assay susceptibility testing isoniazid rifampicin |
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