| BRIEF COMMUNICATION |
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| Year : 2012 | Volume
: 30
| Issue : 1 | Page : 81-84 |
Comparison of the 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide tube method with the conventional method and real-time polymerase chain reaction for the detection of rifampicin resistance in Mycobacterium tuberculosis
U Raut1, S Rantai2, P Narang3, DS Chauhan4, M Chahar4, R Narang3, DK Mendiratta3
1 Departments of Microbiology, Jawaharlal Nehru Medical College, Datta Meghe Institute of Medical Sciences, Sawangi (M), Wardha, Maharashtra, India
2 Departments of Microbiology, Christian Medical College, Ludhiana, Punjab, India
3 Mahatma Gandhi Institute of Medical Sciences, Sewagram, District Wardha, Maharashtra 442 102, India
4 Department of Microbiology and Molecular Biology, National JALMA Institute of Leprosy and Other Mycobacterial Diseases, Dr. M. Miyazaki Marg, Tajganj, Agra, Uttar Pradesh 282 001, India
Correspondence Address:
P Narang
Mahatma Gandhi Institute of Medical Sciences, Sewagram, District Wardha, Maharashtra 442 102
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/0255-0857.93047
Colorimetric methods are cheap, reproducible, and rapid methods of detecting drug resistance in Mycobacterium tuberculosis. The MTT (3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide) method is one such technique that has been established in our laboratory to detect rifampicin resistance. The present study compared the results of the MTT method with those of the proportion method and real-time polymerase chain reaction (RTPCR) in order to establish sensitivity and specificity of MTT. The mutations for rifampicin resistance occur in rpoB gene, and the commonest reported are in codons 526 and 531. Therefore, RTPCR was targeted at these two codons. The concordance of MTT with the proportion method and RTPCR was 94 and 72.77%, respectively, and that of RTPCR with the proportion method was 77.77%. While the study confirmed that the MTT method is a good method for detecting rifampicin resistance, it also brought out the fact that RTPCR when targeted for limited mutations is not a good tool. Either the genotypic method used should target the total 81-bp rpoB genome or methods such as DNA sequencing should be used. For resource-constraint laboratories, the MTT method can be considered as a better choice.
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