Objective: To study the molecular mechanism of multi-drug resistance in M. Tuberculosis, and to develop a new method for detecting genes related with multi-drug resistance.
Method: The ropB, rpsL, katG genes and inhA regulatory sequence in clinical isolates of M. tuberculosis were analyzed with PCR and PCR-SSCP techniques.
Result: The sensitivity of amplifing the drug-resistant genes with PCR was 1-10 pg DNA. Of the 20 multiple resistant strains with reduced sensitivity to streptomycin, rifampin and isoniazid, 90% showed mutations in more than two genetic markers associated with resistance to each of these three drugs, 10% revealed only mutations in rpoB gene.
Conclusion: Multi-drug resistance in M. tuberculosis could be caused by an accumulation of mutations in chromosomal genes encoding drug targets or an alteration at a single multiple resistance locus. PCR and PCR-SSCP techniques might become simple, rapid and reliable diagnostic tests for multi-drug resistance.