Rapid detection of multidrug-resistant Mycobacterium tuberculosis

online | memorias.ioc.fiocruz.br Early detection of drug resistance in Mycobacterium tuberculosis isolates allows for appropriate and timely treatment (Martin et al. 2008). There are many welldefined phenotypic methods for testing the drug susceptibility of M. tuberculosis. The proportion method, performed on Löwenstein-Jensen and 7H10 or 7H11 agar media, is recommended as a reference method. However, this method requires at least three-six weeks to obtain results (Kent & Kubica 1985). There are also rapid automated systems for drug susceptibility testing. The BACTEC 460TB system (Becton Dickinson Diagnostic Systems, Sparks, MD, USA), which is no longer commercially available, is a semi-automated rapid system that is expensive and contains radioactive material. The BACTEC MGIT 960 system (Becton Dickinson Diagnostic Systems) is a non-radiometric rapid automated system. Finally, molecular methods of susceptibility testing are available, including the expensive commercial Xpert MTB/RIF and Genotype MTBDRplus assays (Bwanga et al. 2009, Friedrich et al. 2011, Chang et al. 2012). New rapid, inexpensive, reliable and reproducible colourimetric methods have been recently developed. In particular, the nitrate reductase assay and resazurin microplate method have been commonly used (Angeby et al. 2002, Coban et al. 2004, Martin et al. 2007, 2011, Palomino et al. 2007, WHO 2010). Farnia et al. (2008) reported that the colourimetric malachite green decolourisation assay (MGDA) could be used for the rapid detection of resistance. The aim of this study was to investigate the performance of the MGDA test for the detection of isoniazid (INH) and rifampicin (RIF) resistance in M. tuberculosis clinical isolates.