Rapid detection of rifampicin resistance in sputum and biopsy specimens from tuberculosis patients by PCR and line probe assay

Abstract

Setting: Multidrug resistant Mycobacterium tuberculosis strains are threatening TB control in the world. Rapid diagnosis of resistance is essential for adequate treatment and optimal control of the disease.

Objective: Evaluation of a new technique (Line Probe Assay, LiPA) for easy and rapid detection of Rifampicin resistance (RMPR) of M. tuberculosis.

Design: After amplification of the region of the RNA polymerase, involved in RMPR, the amplified product is hybridized with a set of 10 oligonucleotides immobilized onto a membrane strip. From the pattern obtained the presence or absence of RMPR M. tuberculosis can be assessed. 67 clinical samples positive in culture for M. tuberculosis were analyzed with LiPA and results were compared with classical susceptibility testing.

Results: In vitro drug sensitivity testing identified 46 rifampicin sensitive and 21 resistant strains. In 65 of the 67 specimens LiPA results matched classical testing. In two RMPR cases LiPA showed a sensitive pattern.

Conclusion: In contrast to culture and sensitivity testing, where results take on average 6 weeks, LiPA testing is an easy and rapid (< 48 h) method of detecting RMPR M. tuberculosis in clinical samples. Results correlated in 97% of the samples. In the two RMPR samples with a sensitive LiPA pattern another mechanism of resistance is suspected.