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[Studies on mutation of rifampicin-resistant genes in M. tuberculosis]
Objective:
To understand mutation of rifampicin-resistant genes in M. tuberculosis clinical isolates, and to develop a new method for detecting drug resistance.
Method:
Analyzing the rpoB genes in 50 M. tuberculosis clinical isolates with polymerase chain reaction-single-stranded conformation polymorphism (PCR-SS-CP) and PCR-direct sequencing(PCR-DS) techniques. M. tuberculosis strain H37Rv was used as control.
Result:
Of 3 drug-sensitive isolates and 2 non-rifampicin-resistant isolates selected, only 1 drug-sensitive isolate with abnormal rpoB SSCP profile had TCG-->TTG mutation at codon 531. Of 45 rifampicin-resistant isolates, 35 isolates with abnormal SSCP profiles had mutations in rpoB sequences, in which 14 isolates displayed TCG-->TTG or TGG or TAC mutations at codon 531, 14 had CAC-->TAC or GAC or CCC or CTC or GTC mutations at codon 526, 2 had GAC-->GTC or TAC mutations at codon 516, 2 had two point mutations, and 3 had different rpoB sequences from that of M. tuberculosis.
Conclusion:
Resistance to rifampicin in most M. tuberculosis isolates is due to the mutations on the genes encoding the RNA polymerase subunit (rpoB). PCR-SSCP and PCR-DS techniques might become simple, rapid and reliable diagnostic tests for rifampicin resistance in clinical isolates.