MDR/XDR-TB Colour Test for drug susceptibility testing of Mycobacterium tuberculosis, Northwest Ethiopia.

Abstract Background Appropriate-technology tests are needed for Mycobacterium tuberculosis drug-susceptibility testing (DST) in resource-constrained settings. We evaluated the MDR/XDRTB colour plate thin-layer agar test (TB-CX) for M. tuberculosis DST by directly testing sputum at University of Gondar Hospital. Methods Sputum samples were each divided into 2 aliquots. One aliquot was mixed with disinfectant and applied directly to the TB-CX quadrant petri-plate containing culture medium with and without isoniazid, rifampicin or ciprofloxacin. Concurrently, the other aliquot was decontaminated with sodium hydroxide, centrifuged and cultured on Lowenstein-Jensen media, then the stored M. tuberculosis isolates were sub-cultured in BACTEC™ Mycobacteria Growth Indicator Tube™ (MGIT) 960 for reference DST. Results TB-CX text yielded DST results for 94% (123/131) of positive samples. For paired DST results, median days from sputum processing to DST was 12 for TB-CX versus 35 for LJ-MGIT (P  Conclusion The TB-CX was simple and rapid for M. tuberculosis DST. Discordant DST results may have resulted from sub-optimal storage and different isoniazid concentrations used in TB-CX versus the reference standard test.