Department of Microbiology, Queen Mary Hospital, The University of Hong Kong

Coincident with the resurgence of tuberculosis, there has been an alarming increase in the number and proportion of infections with strains of Mycobacterium tuberculosis that are resistant to two or more of the first line anti-tuberculosis drugs including rifampin and isoniazid. This study aimed at a rapid DNA microarray-based method for detecting mutations in the RNA polymerase beta subunit (rpoB) gene, which confers resistance to rifampin in M. tuberculosis. A total of 62 strains of Mycobacterium tuberculosis and 387 clinical samples were recruited in the study. After amplification of the polymorphic portion the rpoB gene by PCR, the DNA microarray detected 3 types of mutation (D516V, S531L, and H526D). Turnaround time was shortened from 6 weeks to 3 days. Essentially a hybridization technology, DNA microarray can be used to detect all known types of rifampin mutations on single slide coated with 50 probes. It was shown directly applied to clinical specimens with high sensitivity and specificity. As rifampin resistance is a surrogate marker of multi-drug resistant tuberculosis, rapid diagnosis is crucial in early treatment and control of the disease.