Quick assay for drug resistant TB
doi:10.1038/nindia.2011.113 Published online 28 July 2011
Researchers in Mumbai have developed an assay that can rapidly detect drug resistance in TB patients.
TB drug resistance is a stumbling block for healthcare professionals and patients battling the disease. There is currently no cure for some extensively drug-resistant (XDR) strains. Clinical researchers are concerned that such resistance could transmit and necessitate additional controls, rapid diagnostics and newer drugs.
Researchers at the P. D. Hinduja National Hospital and Medical Research Centre developed the in-house assay using the reverse line blot hybridization (RLBH) method to rapidly detect resistance to drugs involved in XDR-TB directly from smear-positive specimens. They collected 215 XDR-TB isolates and 50 pansusceptible isolates for analysis using this assay.
The assay was also successfully applied to 73 smear-positive clinical specimens. The RLBH assay exhibited good sensitivity for the detection of resistance to isoniazid (99%), rifampin (99%), fluoroquinolones (95.3%), and second-line aminoglycosides (94.8%).
Direct smear-positive clinical specimens revealed 93% concordance with the phenotypic drug susceptibility test (DST) results for these drugs.
With the molecular assay, the time to detect drug resistance was reduced to three days from three weeks with conventional methods. This would reduce diagnostic delays in XDR-TB cases significantly, the researchers say.