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.
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Objective To evaluate the application of multiple locus variable number tandem repeat analysis (MLVA, 15-locus set)for genotyping of Mycobacterium tuberculosis (MTB) strains of Beijing genotype. Methods Total 72 Beijing genotype MTB strains obtained from Beijing Thoracic Hospital were genotyped by MLVA (15-locus set). The results were compared with that generated from "gold standard"IS6110-RFLP. Results After genotyped by MLVA ( 15-locus set), 72 strains were grouped into 59 types,of which 53 were unique types. The Hunter-Gaston index (HGI) of MLVA ( 15-locus set) was 0.990. The loci QUB-11b, Mtub 21 and QUB-26 were polymorphic in selected Beijing genotype strains. Genotyping by IS6110-RFLP generated 69 types, of which 66 were unique types. The HGI of IS6110-RFLP was up to 0.999, and the MLVA (15-locus set) clustered strains could be further subdivided. Conclusion MLVA(15-locus set) showed better discriminatory ability in Beijing genotype MTB strains, though secondary typing of clustered strains by IS6110-RFLP is needed.
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Objective To construct fusion gene and prokaryofie expression plasmid encoding the Rv1884c and Rv0867c genes in Mycobacterium tuberculosis (M.tb).The fusion protein wsg expressed efficienfly in E.coli cells.Methods The Rv1884c and Rv0867c genes were amplified by polymerase chain reactions (PCR) with specific primers from genomic DNA of M.tb H37Rv strain,and cloned into pGEX-4Tland pUC19 vectors.Rv1884c and Rv0867c were subcloned into the expression vector pGEX-4T-1 and pPRO-EXHT followed by DNA sequencing.The plasmids were transformed into E.coli DH5α and induced to produce GST-fused Rv1884c and His-fused Rv0867c fusion protein.The protein molecular weight and expression format was analyzed by SDS-PAGE.Results The recombinant expressive vectors pGEX-4T-1Rv1884c and pPRO-EXHT-Rv0867c were constructed.The DH5α strains of E.coli with recombinant plasmid showed high level of Rv1884c and Rv0867c gene expressions after IPTG induction.The SDS-PAGE showed that the plasmids expressed Rv1884c and Rv0867c fusion proteins with molecule weight of 45 000 and 80 000.The recombinant protein accounted for 18.3%and 23.7%of total bacteria protein.The expressed proteins could be purified via GSTrao FF and Ni2+-NTA system kits in denatured condition.Conclusions Mycobacterium tuberculosis Rv1884e and Rv0867c genes have been cloned and expressed Successfully in E.coli DH5α.The results lay a basis for further study of fast culfivation in Mycobacterium tuberculosis and investigation of their activities and functions.