A new multiplex-polymerase chain reaction-single strand conformation polymorphism assay for simultaneous detection of isoniazid and rifampin resistance in Mycobacterium tuberculosis

Abstract

Objective To detect the isoniazid (INH) and rifampin (RIF) resistance of Mycohaeterium tuberculosis isolates in the single tube with multiplex-polymerase chain reaction-single strand conformation polymorphism(muhi-PCR-SSCP) system. Methods According to the sequences of inhA, katG and rpoB genes of the Mycohacterium tuberculosis, three pairs of oligonucleotide primes were designed to examine the INH and RIF resistance with the multi-PCR-SSCP. The validity of the newly developed method was evaluated with 116 clinical isolates of Mycohacterium tuberculosis( 70 isolates that were INH-resistant and 66 isolates that were RIF-resistant). Results The validity of the method was assessed with multiplex PCR-SSCP with the bacteria culture with susceptibility test as golden standard. The three genes, katG, inhA and rpoB, in the 116 clinical isolates and H37Rv strain were amplified successfully in single PCR reactions,except 4 isolates with katG deletion mutants. Compared with strain H37Rv, forty-six isolates had katG gene mutations, thirteen had inhA mutations and fifty-eight had rpoB mutations. Thirty-eight isolates had simultaneous katG and rpoB mutations and 4 isolates had both inhA and rpoB mutations. Four isolates had inhA and katG mutations and 2 isolates had mutations in all three genes simultaneously. The sensitivity of the newly developed multiplex-PCR-SSCP assay was 80% and 82% for INH and RIF, respectively. The specificity of the assay was 100% and 92% for INH and RIF, respectively. Conclusion Muhiplex-PCRSSCP provides a rapid, specific and cost-effective method of detecting multidrug-resistant TB. It laid a solid foundation for the further study of drug resistant gene. Key words: Myeobacterium tuberculosis; Drug resistance,multiple,bacterial; Polymerase chain reaction; Polymorphism,single-strandod conformational