Evaluation of five colorimetric methods for rapid detection of multidrug-resistant Mycobacterium tuberculosis isolates.

AIMS: Tuberculosis (TB) continues to pose a major threat to global public health, particularly due to the increasing prevalence of antimicrobial resistance. This study aimed to evaluate the performance of five different colorimetric drug susceptibility testing (DST) methods, including a newly developed assay.

METHODS

A total of 56 clinical Mycobacterium tuberculosis strains with varying resistance profiles, along with two ATCC reference strains, were tested against four first-line anti-TB antibiotics: isoniazid (INH), rifampicin (RIF), streptomycin (STR), and ethambutol (EMB). The assays NRTA, CRTA, CVDTA, MGDTA, and a newly developed disk-based resazurin tube assay (DBRTA) were performed in Middlebrook 7H9 broth at standard critical drug concentrations. Results were compared against the BACTEC MGIT 960 system as the reference method.

RESULTS

The DST results were obtained within 7 to 14 days. The overall agreement with the reference method was 96.87 % for NRTA, 95.08 % for CRTA, 93.75 % for both CVDTA and MGDTA, and 95.53 % for DBRTA.

CONCLUSIONS

Colorimetric assays, especially DBRTA, offer cost-effective, rapid, and scalable solutions for MDR-TB detection. Their simplicity and affordability make them particularly suitable for routine use in resource-limited settings, contributing to improved TB management and global control efforts.