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 ORIGINAL ARTICLE
Year : 2010  |  Volume : 28  |  Issue : 3  |  Page : 211-216

Detection of Mycobacterium tuberculosis resistance mutations to rifampin and isoniazid by real-time PCR


1 'Prof. Dr. Matei Bals' National Institute for Infectious Diseases, Str. Calistrat Grozovici, Nr. 1, Sector 2, 021105 Bucharest, Romania
2 'Marius Nasta' National Institute of Pneumology, Sos. Viilor Nr 90, Sector 5, 050512 Bucharest, Romania
3 Department of Internal Medicine, Colentina Clinical Hospital, Sos. Stefan Cel Mare, 19-21, Sector 2, 020125 Bucharest, Romania

Correspondence Address:
A Hristea
'Prof. Dr. Matei Bals' National Institute for Infectious Diseases, Str. Calistrat Grozovici, Nr. 1, Sector 2, 021105 Bucharest
Romania
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0255-0857.66474

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Objective: The objective of our study was to evaluate the use of a real-time polymerase chain reaction (PCR)-based technique for the prediction of phenotypic resistance of Mycobacterium tuberculosis. Materials and Methods: We tested 67 M tuberculosis strains (26 drug resistant and 41 drug susceptible) using a method recommended for the LightCycler platform. The susceptibility testing was performed by the absolute concentration method. For rifampin resistance, two regions of the rpoB gene were targeted, while for identification of isoniazid resistance, we searched for mutations in katG and inhA genes. Results: The sensitivity and specificity of this method for rapid detection of mutations for isoniazid resistance were 96% (95% CI: 88% to 100%) and 95% (95% CI: 89% to 100%), respectively. For detection of rifampin resistance, the sensitivity and specificity were 92% (95% CI: 81% to 100%) and 74% (95% CI: 61% to 87%), respectively. The main isoniazid resistance mechanism identified in our isolates is related to changes in the katG gene that encodes catalase. We found that for rifampin resistance the concordance between the predicted and observed phenotype was less than satisfactory. Conclusions: Using this method, the best accuracy for genotyping compared with phenotypic resistance testing was obtained for detecting isoniazid resistance mutations. Although real-time PCR assay may be a valuable diagnostic tool, it is not yet completely satisfactory for detection of drug resistance mutations in M tuberculosis.






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2004 - Indian Journal of Medical Microbiology
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