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

Int J Infect Dis. 2020 Jan;90:213-218. doi: 10.1016/j.ijid.2019.10.041. Epub 2019 Nov 2.


Background: Appropriate technology tests are needed for Mycobacterium tuberculosis drug-susceptibility testing (DST) in resource-constrained settings. This study was performed to evaluate the MDR/XDR-TB Colour Test (a colour platethin-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 two 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 Lӧwenstein-Jensen medium; the stored M. tuberculosis isolates were then sub-cultured in BACTEC Mycobacteria Growth Indicator Tube (MGIT) 960 for reference DST.

Results: The TB-CX test yielded DST results for 94% (123/131) of positive samples. For paired DST results, the median number of days from sputum processing to DST was 12 for TB-CX versus 35 for LJ-MGIT (p<0.001). Compared with LJ-MGIT for isoniazid, rifampicin, and multidrug-resistant tuberculosis, TB-CX had 59%, 96%, and 95% sensitivity; 96%, 94%, and 98% specificity; and 85%, 94%, and 98% agreement, respectively. All ciprofloxacin DST results were susceptible by both methods.

Conclusion: The TB-CX test 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.

Keywords: Drug susceptibility testing; Drug-resistant; MDR/XDR-TB Colour Test; Thin-layer agar; Tuberculosis.

MeSH terms

  • Adolescent
  • Adult
  • Antitubercular Agents / pharmacology
  • Ciprofloxacin / pharmacology
  • Culture Media / chemistry
  • Culture Media / metabolism
  • Ethiopia / epidemiology
  • Extensively Drug-Resistant Tuberculosis / diagnosis*
  • Extensively Drug-Resistant Tuberculosis / microbiology
  • Female
  • Health Resources
  • Humans
  • Isoniazid / pharmacology
  • Male
  • Microbial Sensitivity Tests
  • Mycobacterium tuberculosis / drug effects*
  • Mycobacterium tuberculosis / growth & development
  • Mycobacterium tuberculosis / isolation & purification
  • Mycobacterium tuberculosis / metabolism
  • Rifampin / pharmacology
  • Sensitivity and Specificity
  • Sputum / microbiology
  • Tuberculosis, Multidrug-Resistant / diagnosis*
  • Tuberculosis, Multidrug-Resistant / microbiology
  • Young Adult


  • Antitubercular Agents
  • Culture Media
  • Ciprofloxacin
  • Isoniazid
  • Rifampin