<正>Objective: To study the relationship between the polymorphism of drug resistant gene rpoB and drug resistance against rifampicin（RFP） of M. tuberculosis L-forms

and to evaluate its clinical application. Methods: A total of 52 clinical isolated strains of M. tuberculosis L-forms were collected. rpoB gene polymorphism was analyzed by polymerasc chain reaction and single-strand conformation polymorphism （PCR-SSCP） and conventional antimicrobial susceptibility test （AST）. Their results were compared. Results: AST results showed that 38 of 52 clinical isolated strains were drug resistance （73. 08%）

while PCR-SSCP indicated 65. 38% （32/52） rpoB gene polymorphism. There was no statistic significance （X2 = 2. 4914） between the 2 methods. Conclusion:Combined the application of PCR-SSCP with AST in detecting rpoB drug resistant gene polymorphism of M. tuberculosis L-form from pneumoconiosis patients with tuberculosis may have advantages at earlier diagnosis and guidance of clinical medications.