Multicentre laboratory validation of the colorimetric redox indicator (CRI) assay for the rapid detection of extensively drug-resistant (XDR) Mycobacterium tuberculosis

A Martin, F Paasch, S Docx, K Fissette, B Imperiale, W Ribón, LA Gonzalez, J Werngren, A Engström, G Skenders, P Juréen, S Hoffner, P Del Portillo, N Morcillo, JC Palomino

    Research output: Contribution to journalA1: Web of Science-article


    Objectives To perform a multicentre study to evaluate the performance of the colorimetric redox indicator (CRI) assay and to establish the MICs and critical concentrations of rifampicin, isoniazid, ofloxacin, kanamycin and capreomycin. Methods The study was carried out in two phases. Phase I determined the MIC of each drug. Phase II established critical concentrations for the five drugs tested by the CRI assay compared with the conventional proportion method. Results Phase I: a strain was considered resistant by the CRI assay if the MIC was >/=0.5 mg/L for rifampicin, >/=0.25 mg/L for isoniazid, >/=4.0 mg/L for ofloxacin and >/=5.0 mg/L for kanamycin and capreomycin. Sensitivity was 99.1% for isoniazid and 100% for the other drugs and specificity was 97.9% for capreomycin and 100% for the other drugs. Phase II: the critical concentration was 0.5 mg/L for rifampicin, 0.25 mg/L for isoniazid, 2.0 mg/L for ofloxacin and 2.5 mg/L for kanamycin and capreomycin giving an overall accuracy of 98.4%, 96.6%, 96.7%, 98.3% and 90%, respectively. Conclusions Results demonstrate that the CRI assay is an accurate method for the rapid detection of XDR Mycobacterium tuberculosis. The CRI assay is faster than the conventional drug susceptibility testing method using solid medium, has the same turnaround time as the BACTEC MGIT 960 system, but is less expensive, and could be an adequate method for low-income countries.
    Original languageEnglish
    JournalJournal of Antimicrobial Chemotherapy
    Issue number4
    Pages (from-to)827-833
    Publication statusPublished - 2011


    • B780-tropical-medicine
    • Bacterial diseases
    • Tuberculosis
    • Mycobacterium tuberculosis
    • Detection
    • Drug resistance
    • Rapid diagnostic tests
    • Colorimetric methods
    • Assays
    • Laboratory network
    • Validation
    • Rifampicin
    • Isoniazid
    • Ofloxacin
    • Kanamycin
    • Capreomycin
    • BACTEC
    • Specificity
    • Sensitivity
    • Laboratory techniques and procedures


    Dive into the research topics of 'Multicentre laboratory validation of the colorimetric redox indicator (CRI) assay for the rapid detection of extensively drug-resistant (XDR) <i>Mycobacterium tuberculosis</i>'. Together they form a unique fingerprint.

    Cite this